diff --git a/backend/src/backend/experiments/calc_surf_isec_custom.py b/backend/src/backend/experiments/calc_surf_isec_custom.py
index 3d0cd9d36..651d424a5 100644
--- a/backend/src/backend/experiments/calc_surf_isec_custom.py
+++ b/backend/src/backend/experiments/calc_surf_isec_custom.py
@@ -45,11 +45,12 @@ async def calc_surf_isec_custom(
     name: str,
     attribute: str,
     num_reals: int,
+    num_workers: int, 
     cutting_plane: schemas.CuttingPlane,
 ) -> List[schemas.SurfaceIntersectionData]:
     
     myprefix = ">>>>>>>>>>>>>>>>> calc_surf_isec_custom():"
-    print(f"{myprefix} started with {num_reals=}", flush=True)
+    print(f"{myprefix} started with {num_reals=} {num_workers=}", flush=True)
 
     perf_metrics.reset_lap_timer()
 
@@ -63,7 +64,7 @@ async def calc_surf_isec_custom(
     multi_queue = multiprocessing.Queue()
     async_queue = AsyncQueue(multi_queue)
 
-    num_procs=4
+    num_procs=num_workers
     proc_arr = []
     for proc_num in range(num_procs):
         p = multiprocessing.Process(target=process_surf_worker, args=(f"sigworker{proc_num}", multi_queue, fence_arr))
@@ -95,7 +96,8 @@ async def calc_surf_isec_custom(
 
 async def load_surf_bytes_task(queue, access: SurfaceAccess, real_num: int, name: str, attribute: str):
     surf_bytes = await access.get_realization_surface_bytes_async(real_num=real_num, name=name, attribute=attribute)
-    await queue.put(surf_bytes)
+    if surf_bytes is not None:
+        await queue.put(surf_bytes)
 
 
 def process_surf_worker(workerName, queue, fence_arr):
diff --git a/backend/src/backend/user_session/routers/surface/router.py b/backend/src/backend/user_session/routers/surface/router.py
index 1dde05f33..cbb7bb898 100644
--- a/backend/src/backend/user_session/routers/surface/router.py
+++ b/backend/src/backend/user_session/routers/surface/router.py
@@ -61,7 +61,7 @@ async def post_calc_surf_isec_experiments(
     #intersections = await calc_surf_isec_fetch_first(perf_metrics, authenticated_user, case_uuid, ensemble_name, name, attribute, num_reals, cutting_plane)
     #intersections = await calc_surf_isec_queue(perf_metrics, authenticated_user, case_uuid, ensemble_name, name, attribute, num_reals, num_workers, cutting_plane)
     #intersections = await calc_surf_isec_multiprocess(perf_metrics, authenticated_user, case_uuid, ensemble_name, name, attribute, num_reals, cutting_plane)
-    intersections = await calc_surf_isec_custom(perf_metrics, authenticated_user, case_uuid, ensemble_name, name, attribute, num_reals, cutting_plane)
+    intersections = await calc_surf_isec_custom(perf_metrics, authenticated_user, case_uuid, ensemble_name, name, attribute, num_reals, num_workers, cutting_plane)
 
     LOGGER.debug(f"route calc_surf_isec_experiments - intersected {len(intersections)} surfaces in: {perf_metrics.to_string()}")