diff --git a/mpcontribs-client/mpcontribs/client/__init__.py b/mpcontribs-client/mpcontribs/client/__init__.py
index 9f3666364..3f16c49ca 100644
--- a/mpcontribs-client/mpcontribs/client/__init__.py
+++ b/mpcontribs-client/mpcontribs/client/__init__.py
@@ -953,7 +953,11 @@ def _get_future(
         setattr(future, "track_id", track_id)
         return future
 
-    def available_query_params(self, resource="contributions"):
+    def available_query_params(
+        self,
+        startswith: tuple = None,
+        resource: str = "contributions"
+    ) -> list:
         resources = self.swagger_spec.resources
         resource_obj = resources.get(resource)
         if not resource_obj:
@@ -962,7 +966,14 @@ def available_query_params(self, resource="contributions"):
 
         op_key = f"query{resource.capitalize()}"
         operation = resource_obj.operations[op_key]
-        return [param.name for param in operation.params.values()]
+        params = [param.name for param in operation.params.values()]
+        if not startswith:
+            return params
+
+        return [
+            param for param in params
+            if param.startswith(startswith)
+        ]
 
     def get_project(self, name: str = None, fields: list = None) -> Type[Dict]:
         """Retrieve a project entry
@@ -1093,14 +1104,17 @@ def update_project(self, update: dict, name: str = None):
             raise MPContribsClientError("initialize client with project or set `name` argument!")
 
         disallowed = ["is_approved", "stats", "columns", "is_public", "owner"]
-        for k in disallowed:
-            if k in update:
+        for k in list(update.keys()):
+            if k in disallowed:
                 logger.warning(f"removing `{k}` from update - not allowed.")
                 update.pop(k)
                 if k == "columns":
                     logger.info("use `client.init_columns()` to update project columns.")
                 elif k == "is_public":
                     logger.info("use `client.make_public/private()` to set `is_public`.")
+            elif not isinstance(update[k], bool) and not update[k]:
+                logger.warning(f"removing `{k}` from update - no update requested.")
+                update.pop(k)
 
         if not update:
             logger.warning("nothing to update")
@@ -1121,7 +1135,7 @@ def update_project(self, update: dict, name: str = None):
 
         payload = {
             k: v for k, v in update.items()
-            if v and k in fields and project.get(k, None) != v
+            if k in fields and project.get(k, None) != v
         }
         if not payload:
             logger.warning("nothing to update")
@@ -1469,6 +1483,10 @@ def get_totals(
 
         return result["total_count"], result["total_pages"]
 
+    def count(self, query: dict = None) -> int:
+        """shortcut for get_totals()"""
+        return self.get_totals(query=query)[0]
+
     def get_unique_identifiers_flags(self, query: dict = None) -> dict:
         """Retrieve values for `unique_identifiers` flags.
 
@@ -2060,6 +2078,7 @@ def submit_contributions(
         # submit contributions
         if contribs:
             total, total_processed = 0, 0
+            nmax = 1000  # TODO this should be set dynamically from `bulk_update_limit`
 
             def post_future(track_id, payload):
                 future = self.session.post(
@@ -2101,8 +2120,9 @@ def put_future(pk, payload):
                             else:
                                 logger.error(f"SKIPPED: update of {project_name}/{pk} too large.")
                         else:
-                            next_payload = ujson.dumps(post_chunk + [c]).encode("utf-8")
-                            if len(next_payload) >= MAX_PAYLOAD:
+                            next_post_chunk = post_chunk + [c]
+                            next_payload = ujson.dumps(next_post_chunk).encode("utf-8")
+                            if len(next_post_chunk) > nmax or len(next_payload) >= MAX_PAYLOAD:
                                 if post_chunk:
                                     payload = ujson.dumps(post_chunk).encode("utf-8")
                                     futures.append(post_future(idx, payload))