diff --git a/adapters-api/src/main/java/io/nosqlbench/engine/api/activityimpl/OpMapper.java b/adapters-api/src/main/java/io/nosqlbench/engine/api/activityimpl/OpMapper.java
index 93a09a086..268647cb4 100644
--- a/adapters-api/src/main/java/io/nosqlbench/engine/api/activityimpl/OpMapper.java
+++ b/adapters-api/src/main/java/io/nosqlbench/engine/api/activityimpl/OpMapper.java
@@ -53,7 +53,7 @@ import java.util.function.Function;
  * rules provided to the user. Conversely, the driver maintainer should take care to provide
  * rules of construction and examples in the documentation.
  * Each {@link io.nosqlbench.engine.api.activityimpl.uniform.DriverAdapter} has a unique
- * name, just as with {@link io.nosqlbench.engine.api.activityapi.core.ActivityType}s. The documentation
+ * name. The documentation
  * for each of these should be kept in the bundled resources in a top-level markdown file that
  * matches the driver name.
  * </p>
@@ -62,7 +62,7 @@ import java.util.function.Function;
  *            to hold all the details for executing an operation,
  *            generally something that implements {@link Runnable}.
  */
-public interface OpMapper<T extends Op> extends Function<ParsedOp, OpDispenser<T>> {
+public interface OpMapper<T extends Op> extends Function<ParsedOp, OpDispenser<? extends T>> {
 
     /**
      * Interrogate the parsed command, and provide a new
@@ -73,5 +73,5 @@ public interface OpMapper<T extends Op> extends Function<ParsedOp, OpDispenser<T
      * @return An OpDispenser which can be used to synthesize real operations.
      */
     @Override
-    OpDispenser<T> apply(ParsedOp cmd);
+    OpDispenser<? extends T> apply(ParsedOp cmd);
 }
diff --git a/driver-http/src/main/java/io/nosqlbench/activitytype/cmds/HttpAsyncOp.java b/driver-http/src/main/java/io/nosqlbench/activitytype/cmds/HttpAsyncOp.java
index 55f2afff5..99c15a252 100644
--- a/driver-http/src/main/java/io/nosqlbench/activitytype/cmds/HttpAsyncOp.java
+++ b/driver-http/src/main/java/io/nosqlbench/activitytype/cmds/HttpAsyncOp.java
@@ -7,13 +7,13 @@ import java.util.function.LongFunction;
 
 public class HttpAsyncOp {
     public final HttpAsyncAction action;
-    public final LongFunction<HttpOp> op;
+    public final LongFunction<? extends HttpOp> op;
     public final long cycle;
 
     private final HttpOp httpOp;
     private final HttpClient client;
 
-    public HttpAsyncOp(HttpAsyncAction action, LongFunction<HttpOp> op, long cycle, HttpClient client) {
+    public HttpAsyncOp(HttpAsyncAction action, LongFunction<? extends HttpOp> op, long cycle, HttpClient client) {
         this.action = action;
         this.op = op;
         this.cycle = cycle;
diff --git a/driver-http/src/main/java/io/nosqlbench/activitytype/http/HttpAction.java b/driver-http/src/main/java/io/nosqlbench/activitytype/http/HttpAction.java
index 0ab9c7265..804de49cf 100644
--- a/driver-http/src/main/java/io/nosqlbench/activitytype/http/HttpAction.java
+++ b/driver-http/src/main/java/io/nosqlbench/activitytype/http/HttpAction.java
@@ -30,7 +30,7 @@ public class HttpAction implements SyncAction {
     private final int slot;
     private int maxTries = 1;
 
-    private OpSequence<OpDispenser<HttpOp>> sequencer;
+    private OpSequence<OpDispenser<? extends HttpOp>> sequencer;
     private HttpClient client;
 
     private final HttpResponse.BodyHandler<String> bodyreader = HttpResponse.BodyHandlers.ofString();
@@ -62,7 +62,7 @@ public class HttpAction implements SyncAction {
         // operation for execution, including data generation as well as
         // op construction
         try (Timer.Context bindTime = httpActivity.bindTimer.time()) {
-            LongFunction<HttpOp> readyOp = sequencer.apply(cycle);
+            LongFunction<? extends HttpOp> readyOp = sequencer.apply(cycle);
             httpOp = readyOp.apply(cycle);
         } catch (Exception e) {
             if (httpActivity.isDiagnosticMode()) {
diff --git a/driver-http/src/main/java/io/nosqlbench/activitytype/http/HttpActivity.java b/driver-http/src/main/java/io/nosqlbench/activitytype/http/HttpActivity.java
index 0c3b1267d..e159ff3ea 100644
--- a/driver-http/src/main/java/io/nosqlbench/activitytype/http/HttpActivity.java
+++ b/driver-http/src/main/java/io/nosqlbench/activitytype/http/HttpActivity.java
@@ -37,7 +37,7 @@ public class HttpActivity extends SimpleActivity implements Activity, ActivityDe
     public Timer resultSuccessTimer;
     public Histogram statusCodeHisto;
 
-    private OpSequence<OpDispenser<HttpOp>> sequencer;
+    private OpSequence<OpDispenser<? extends HttpOp>> sequencer;
     private boolean diagnosticsEnabled;
     private long timeout = Long.MAX_VALUE;
     private NBErrorHandler errorhandler;
@@ -121,7 +121,7 @@ public class HttpActivity extends SimpleActivity implements Activity, ActivityDe
         return builder.build();
     }
 
-    public OpSequence<OpDispenser<HttpOp>> getSequencer() {
+    public OpSequence<OpDispenser<? extends HttpOp>> getSequencer() {
         return sequencer;
     }
 
diff --git a/driver-http/src/main/java/io/nosqlbench/activitytype/http/async/HttpAsyncAction.java b/driver-http/src/main/java/io/nosqlbench/activitytype/http/async/HttpAsyncAction.java
index 2fbcb7999..ea6e68918 100644
--- a/driver-http/src/main/java/io/nosqlbench/activitytype/http/async/HttpAsyncAction.java
+++ b/driver-http/src/main/java/io/nosqlbench/activitytype/http/async/HttpAsyncAction.java
@@ -19,7 +19,7 @@ public class HttpAsyncAction extends BaseAsyncAction<HttpAsyncOp, HttpActivity>
 
     private final static Logger logger = LogManager.getLogger(HttpAsyncAction.class);
 
-    private OpSequence<OpDispenser<HttpOp>> sequencer;
+    private OpSequence<OpDispenser<? extends HttpOp>> sequencer;
     private HttpClient client;
 
     private CompletableFuture<HttpResponse<Void>> future;
@@ -46,7 +46,7 @@ public class HttpAsyncAction extends BaseAsyncAction<HttpAsyncOp, HttpActivity>
     @Override
     public LongFunction<HttpAsyncOp> getOpInitFunction() {
         return l -> {
-            LongFunction<HttpOp> readyHttpOp = sequencer.apply(l);
+            LongFunction<? extends HttpOp> readyHttpOp = sequencer.apply(l);
             return new HttpAsyncOp(this,readyHttpOp,l,client);
         };
     }
diff --git a/driver-jdbc/src/main/java/io/nosqlbench/activitytype/jdbc/api/JDBCActivity.java b/driver-jdbc/src/main/java/io/nosqlbench/activitytype/jdbc/api/JDBCActivity.java
index 5e13d7d30..4b6f17dec 100644
--- a/driver-jdbc/src/main/java/io/nosqlbench/activitytype/jdbc/api/JDBCActivity.java
+++ b/driver-jdbc/src/main/java/io/nosqlbench/activitytype/jdbc/api/JDBCActivity.java
@@ -29,7 +29,7 @@ public abstract class JDBCActivity extends SimpleActivity {
     private int minRetryDelayMs;
 
     protected DataSource dataSource;
-    protected OpSequence<OpDispenser<String>> opSequence;
+    protected OpSequence<OpDispenser<? extends String>> opSequence;
 
     public JDBCActivity(ActivityDef activityDef) {
         super(activityDef);
@@ -107,7 +107,7 @@ public abstract class JDBCActivity extends SimpleActivity {
         return dataSource;
     }
 
-    public OpSequence<OpDispenser<String>> getOpSequence() {
+    public OpSequence<OpDispenser<? extends String>> getOpSequence() {
         return opSequence;
     }
 
diff --git a/driver-jdbc/src/main/java/io/nosqlbench/activitytype/jdbc/impl/JDBCAction.java b/driver-jdbc/src/main/java/io/nosqlbench/activitytype/jdbc/impl/JDBCAction.java
index e6c8e96d8..616d0f736 100644
--- a/driver-jdbc/src/main/java/io/nosqlbench/activitytype/jdbc/impl/JDBCAction.java
+++ b/driver-jdbc/src/main/java/io/nosqlbench/activitytype/jdbc/impl/JDBCAction.java
@@ -18,7 +18,7 @@ public class JDBCAction implements SyncAction {
     private static final Logger LOGGER = LogManager.getLogger(JDBCAction.class);
 
     private final JDBCActivity activity;
-    private OpSequence<OpDispenser<String>> sequencer;
+    private OpSequence<OpDispenser<? extends String>> sequencer;
 
     public JDBCAction(JDBCActivity a, int slot) {
         activity = a;
@@ -33,7 +33,7 @@ public class JDBCAction implements SyncAction {
     public int runCycle(long cycle) {
         String boundStmt;
 
-        LongFunction<String> unboundStmt = sequencer.apply(cycle);
+        LongFunction<? extends String> unboundStmt = sequencer.apply(cycle);
 
         try (Timer.Context bindTime = activity.getBindTimer().time()) {
             boundStmt = unboundStmt.apply(cycle);
diff --git a/driver-jms/src/main/java/io/nosqlbench/driver/jms/JmsAction.java b/driver-jms/src/main/java/io/nosqlbench/driver/jms/JmsAction.java
index b8f28e064..4b17ca353 100644
--- a/driver-jms/src/main/java/io/nosqlbench/driver/jms/JmsAction.java
+++ b/driver-jms/src/main/java/io/nosqlbench/driver/jms/JmsAction.java
@@ -36,7 +36,7 @@ public class JmsAction implements SyncAction {
 
         JmsOp jmsOp;
         try (Timer.Context ctx = activity.getBindTimer().time()) {
-            LongFunction<JmsOp> readyJmsOp = activity.getSequencer().apply(cycle);
+            LongFunction<? extends JmsOp> readyJmsOp = activity.getSequencer().apply(cycle);
             jmsOp = readyJmsOp.apply(cycle);
         } catch (Exception bindException) {
             // if diagnostic mode ...
diff --git a/driver-jms/src/main/java/io/nosqlbench/driver/jms/JmsActivity.java b/driver-jms/src/main/java/io/nosqlbench/driver/jms/JmsActivity.java
index 39ac5b42d..f22e2b203 100644
--- a/driver-jms/src/main/java/io/nosqlbench/driver/jms/JmsActivity.java
+++ b/driver-jms/src/main/java/io/nosqlbench/driver/jms/JmsActivity.java
@@ -32,7 +32,7 @@ public class JmsActivity extends SimpleActivity {
 
     private JMSContext jmsContext;
 
-    private OpSequence<OpDispenser<JmsOp>> sequence;
+    private OpSequence<OpDispenser<? extends JmsOp>> sequence;
     private volatile Throwable asyncOperationFailure;
     private NBErrorHandler errorhandler;
 
@@ -144,7 +144,7 @@ public class JmsActivity extends SimpleActivity {
 
     @Override
     public synchronized void onActivityDefUpdate(ActivityDef activityDef) { super.onActivityDefUpdate(activityDef); }
-    public OpSequence<OpDispenser<JmsOp>> getSequencer() { return sequence; }
+    public OpSequence<OpDispenser<? extends JmsOp>> getSequencer() { return sequence; }
 
     public String getJmsProviderType() { return jmsProviderType; }
     public JmsConnInfo getJmsConnInfo() { return jmsConnInfo; }
diff --git a/driver-jmx/src/main/java/io/nosqlbench/driver/jmx/JMXAction.java b/driver-jmx/src/main/java/io/nosqlbench/driver/jmx/JMXAction.java
index 88134d288..a0ed2e6f4 100644
--- a/driver-jmx/src/main/java/io/nosqlbench/driver/jmx/JMXAction.java
+++ b/driver-jmx/src/main/java/io/nosqlbench/driver/jmx/JMXAction.java
@@ -17,7 +17,7 @@ public class JMXAction implements SyncAction {
     private final ActivityDef activityDef;
     private final int slot;
     private final JMXActivity activity;
-    private OpSequence<OpDispenser<JmxOp>> sequencer;
+    private OpSequence<OpDispenser<? extends JmxOp>> sequencer;
 
     public JMXAction(ActivityDef activityDef, int slot, JMXActivity activity) {
         this.activityDef = activityDef;
@@ -32,7 +32,7 @@ public class JMXAction implements SyncAction {
 
     @Override
     public int runCycle(long cycle) {
-        LongFunction<JmxOp> readyJmxOp = sequencer.apply(cycle);
+        LongFunction<? extends JmxOp> readyJmxOp = sequencer.apply(cycle);
         JmxOp jmxOp = readyJmxOp.apply(cycle);
         jmxOp.execute();
         return 0;
diff --git a/driver-jmx/src/main/java/io/nosqlbench/driver/jmx/JMXActivity.java b/driver-jmx/src/main/java/io/nosqlbench/driver/jmx/JMXActivity.java
index 193884cbd..87a5da0b3 100644
--- a/driver-jmx/src/main/java/io/nosqlbench/driver/jmx/JMXActivity.java
+++ b/driver-jmx/src/main/java/io/nosqlbench/driver/jmx/JMXActivity.java
@@ -13,7 +13,7 @@ import javax.net.ssl.SSLContext;
 
 public class JMXActivity extends SimpleActivity implements Activity {
 
-    private OpSequence<OpDispenser<JmxOp>> sequence;
+    private OpSequence<OpDispenser<? extends JmxOp>> sequence;
     private SSLContext sslContext;
 
     public JMXActivity(ActivityDef activityDef) {
@@ -39,7 +39,7 @@ public class JMXActivity extends SimpleActivity implements Activity {
         return sslContext;
     }
 
-    public OpSequence<OpDispenser<JmxOp>> getSequencer() {
+    public OpSequence<OpDispenser<? extends JmxOp>> getSequencer() {
         return sequence;
     }
 }
diff --git a/driver-pulsar/src/main/java/io/nosqlbench/driver/pulsar/PulsarAction.java b/driver-pulsar/src/main/java/io/nosqlbench/driver/pulsar/PulsarAction.java
index ee87a3e49..c45a7ded4 100644
--- a/driver-pulsar/src/main/java/io/nosqlbench/driver/pulsar/PulsarAction.java
+++ b/driver-pulsar/src/main/java/io/nosqlbench/driver/pulsar/PulsarAction.java
@@ -37,7 +37,7 @@ public class PulsarAction implements SyncAction {
 
         PulsarOp pulsarOp;
         try (Timer.Context ctx = activity.getBindTimer().time()) {
-            LongFunction<PulsarOp> readyPulsarOp = activity.getSequencer().apply(cycle);
+            LongFunction<? extends PulsarOp> readyPulsarOp = activity.getSequencer().apply(cycle);
             pulsarOp = readyPulsarOp.apply(cycle);
         } catch (Exception bindException) {
             // if diagnostic mode ...
diff --git a/driver-pulsar/src/main/java/io/nosqlbench/driver/pulsar/PulsarActivity.java b/driver-pulsar/src/main/java/io/nosqlbench/driver/pulsar/PulsarActivity.java
index d2e9dc71e..08e383948 100644
--- a/driver-pulsar/src/main/java/io/nosqlbench/driver/pulsar/PulsarActivity.java
+++ b/driver-pulsar/src/main/java/io/nosqlbench/driver/pulsar/PulsarActivity.java
@@ -66,7 +66,7 @@ public class PulsarActivity extends SimpleActivity implements ActivityDefObserve
     private Schema<?> pulsarSchema;
 
     private NBErrorHandler errorHandler;
-    private OpSequence<OpDispenser<PulsarOp>> sequencer;
+    private OpSequence<OpDispenser<? extends PulsarOp>> sequencer;
     private volatile Throwable asyncOperationFailure;
     private boolean cycleratePerThread;
 
@@ -151,7 +151,7 @@ public class PulsarActivity extends SimpleActivity implements ActivityDefObserve
 
     public NBErrorHandler getErrorHandler() { return errorHandler; }
 
-    public OpSequence<OpDispenser<PulsarOp>> getSequencer() { return sequencer; }
+    public OpSequence<OpDispenser<? extends PulsarOp>> getSequencer() { return sequencer; }
 
     public void failOnAsyncOperationFailure() {
         if (asyncOperationFailure != null) {
diff --git a/engine-api/src/main/java/io/nosqlbench/engine/api/activityapi/planning/OpSource.java b/engine-api/src/main/java/io/nosqlbench/engine/api/activityapi/planning/OpSource.java
index 081342f40..b9be3a543 100644
--- a/engine-api/src/main/java/io/nosqlbench/engine/api/activityapi/planning/OpSource.java
+++ b/engine-api/src/main/java/io/nosqlbench/engine/api/activityapi/planning/OpSource.java
@@ -13,7 +13,7 @@ import java.util.function.LongFunction;
  */
 public interface OpSource<T> extends LongFunction<T> {
 
-    static <O extends Op> OpSource<O> of(OpSequence<OpDispenser<O>> seq) {
+    static <O extends Op> OpSource<O> of(OpSequence<OpDispenser<? extends O>> seq) {
         return (long l) -> seq.apply(l).apply(l);
     }
 
diff --git a/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/SimpleActivity.java b/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/SimpleActivity.java
index f132e9671..4b403c40e 100644
--- a/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/SimpleActivity.java
+++ b/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/SimpleActivity.java
@@ -419,20 +419,20 @@ public class SimpleActivity implements Activity, ProgressCapable {
      * @param <O>
      * @return
      */
-    protected <O extends Op> OpSequence<OpDispenser<O>> createOpSequenceFromCommands(Function<CommandTemplate, OpDispenser<O>> opinit) {
+    protected <O extends Op> OpSequence<OpDispenser<? extends O>> createOpSequenceFromCommands(Function<CommandTemplate, OpDispenser<O>> opinit) {
         Function<OpTemplate, CommandTemplate> f = CommandTemplate::new;
-        Function<OpTemplate, OpDispenser<O>> opTemplateOFunction = f.andThen(opinit);
+        Function<OpTemplate, OpDispenser<? extends O>> opTemplateOFunction = f.andThen(opinit);
 
         return createOpSequence(opTemplateOFunction);
     }
 
-    protected <O extends Op> OpSequence<OpDispenser<O>> createOpSourceFromCommands(
-        Function<ParsedOp, OpDispenser<O>> opinit,
+    protected <O extends Op> OpSequence<OpDispenser<? extends O>> createOpSourceFromCommands(
+        Function<ParsedOp, OpDispenser<? extends O>> opinit,
         NBConfiguration cfg,
         List<Function<Map<String, Object>, Map<String, Object>>> parsers
     ) {
         Function<OpTemplate, ParsedOp> f = t -> new ParsedOp(t, cfg, parsers);
-        Function<OpTemplate, OpDispenser<O>> opTemplateOFunction = f.andThen(opinit);
+        Function<OpTemplate, OpDispenser<? extends O>> opTemplateOFunction = f.andThen(opinit);
         return createOpSequence(opTemplateOFunction);
     }
 
@@ -459,14 +459,14 @@ public class SimpleActivity implements Activity, ProgressCapable {
      * @return The sequence of operations as determined by filtering and ratios
      */
     @Deprecated(forRemoval = true)
-    protected <O> OpSequence<OpDispenser<O>> createOpSequence(Function<OpTemplate, OpDispenser<O>> opinit) {
+    protected <O> OpSequence<OpDispenser<? extends O>> createOpSequence(Function<OpTemplate, OpDispenser<? extends O>> opinit) {
         String tagfilter = activityDef.getParams().getOptionalString("tags").orElse("");
-        StrInterpolator interp = new StrInterpolator(activityDef);
+//        StrInterpolator interp = new StrInterpolator(activityDef);
         SequencerType sequencerType = getParams()
             .getOptionalString("seq")
             .map(SequencerType::valueOf)
             .orElse(SequencerType.bucket);
-        SequencePlanner<OpDispenser<O>> planner = new SequencePlanner<>(sequencerType);
+        SequencePlanner<OpDispenser<? extends O>> planner = new SequencePlanner<>(sequencerType);
 
         StmtsDocList stmtsDocList = null;
 
@@ -475,10 +475,10 @@ public class SimpleActivity implements Activity, ProgressCapable {
         Optional<String> stmt = activityDef.getParams().getOptionalString("op", "stmt", "statement");
         Optional<String> op_yaml_loc = activityDef.getParams().getOptionalString("yaml", "workload");
         if (stmt.isPresent()) {
-            stmtsDocList = StatementsLoader.loadStmt(logger, stmt.get(), interp);
+            stmtsDocList = StatementsLoader.loadStmt(logger, stmt.get(), activityDef.getParams());
             workloadSource = "commandline:" + stmt.get();
         } else if (op_yaml_loc.isPresent()) {
-            stmtsDocList = StatementsLoader.loadPath(logger, op_yaml_loc.get(), interp, "activities");
+            stmtsDocList = StatementsLoader.loadPath(logger, op_yaml_loc.get(), activityDef.getParams(), "activities");
             workloadSource = "yaml:" + op_yaml_loc.get();
         }
 
@@ -500,7 +500,7 @@ public class SimpleActivity implements Activity, ProgressCapable {
             for (int i = 0; i < stmts.size(); i++) {
                 long ratio = ratios.get(i);
                 OpTemplate optemplate = stmts.get(i);
-                OpDispenser<O> driverSpecificReadyOp = opinit.apply(optemplate);
+                OpDispenser<? extends O> driverSpecificReadyOp = opinit.apply(optemplate);
                 planner.addOp(driverSpecificReadyOp, ratio);
             }
         } catch (Exception e) {
diff --git a/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/uniform/StandardActivity.java b/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/uniform/StandardActivity.java
index 0d377d29b..6b96dd869 100644
--- a/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/uniform/StandardActivity.java
+++ b/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/uniform/StandardActivity.java
@@ -5,9 +5,9 @@ import io.nosqlbench.engine.api.activityapi.planning.OpSequence;
 import io.nosqlbench.engine.api.activityapi.planning.OpSource;
 import io.nosqlbench.engine.api.activityimpl.ActivityDef;
 import io.nosqlbench.engine.api.activityimpl.OpDispenser;
+import io.nosqlbench.engine.api.activityimpl.OpMapper;
 import io.nosqlbench.engine.api.activityimpl.SimpleActivity;
 import io.nosqlbench.engine.api.activityimpl.uniform.flowtypes.Op;
-import io.nosqlbench.engine.api.templating.ParsedOp;
 import io.nosqlbench.nb.api.errors.OpConfigError;
 
 import java.util.List;
@@ -27,14 +27,15 @@ public class StandardActivity<R extends Op, S> extends SimpleActivity {
     private final DriverAdapter<R, S> adapter;
     private final OpSource<R> opsource;
     private NBErrorHandler errorHandler;
-    private final OpSequence<OpDispenser<R>> sequence;
+    private final OpSequence<OpDispenser<? extends R>> sequence;
 
     public StandardActivity(DriverAdapter<R, S> adapter, ActivityDef activityDef) {
         super(activityDef);
         this.adapter = adapter;
 
         try {
-            Function<ParsedOp, OpDispenser<R>> opmapper = adapter.getOpMapper();
+//            Function<ParsedOp, OpDispenser<R>> opmapper;
+            OpMapper<R> opmapper = adapter.getOpMapper();
             Function<Map<String, Object>, Map<String, Object>> preprocessor = adapter.getPreprocessor();
             sequence = createOpSourceFromCommands(opmapper, adapter.getConfiguration(), List.of(preprocessor));
             opsource = OpSource.of(sequence);
@@ -53,7 +54,7 @@ public class StandardActivity<R extends Op, S> extends SimpleActivity {
         setDefaultsFromOpSequence(sequence);
     }
 
-    public OpSequence<OpDispenser<R>> getOpSequence() {
+    public OpSequence<OpDispenser<? extends R>> getOpSequence() {
         return sequence;
     }