diff --git a/xfel/command_line/striping.py b/xfel/command_line/striping.py
index ea63a8d220..a6c0dc2c30 100644
--- a/xfel/command_line/striping.py
+++ b/xfel/command_line/striping.py
@@ -9,6 +9,7 @@
 # dials.combine_experiments (optionally with clustering and selecting clusters).
 #
 from dials.util import show_mail_on_error
+from dxtbx.model import ExperimentList
 from libtbx.phil import parse
 from libtbx.utils import Sorry
 from libtbx import easy_run
@@ -22,7 +23,11 @@
 
 multiprocessing_override_str = '''
 mp {
+  method = local
   use_mpi = False
+  mpi_command = source
+  mpi_option = ""
+  local.include_mp_in_command = False
 }
 '''
 
@@ -47,7 +52,7 @@
     .help = "Enable to select results evenly spaced across each rungroup"
             "(stripes) as opposed to contiguous chunks."
   chunk_size = 1000
-    .type = float
+    .type = int(value_min=1)
     .help = "Maximum number of images per chunk or stripe."
   respect_rungroup_barriers = True
     .type = bool
@@ -243,6 +248,46 @@
 for interactive unit cell clustering, use combine_experiments.clustering.dendrogram=True
 """
 
+
+def chunk_pairs(expt_paths, refl_paths, max_size=1000):
+  """Distribute matching expt-refl pairs into chunks with < `max_size` expts"""
+  expt_lengths = [len(ExperimentList.from_file(expt_path, check_format=False))
+                  for expt_path in expt_paths]
+  chunk_count = math.ceil(sum(expt_lengths) / max_size)
+  estimated_fill = sum(expt_lengths) / chunk_count
+  chunks_indices = [[] for _ in range(chunk_count)]
+  chunk_lengths = [0] * chunk_count
+  currently_filled_chunk = 0
+  for len_index, len_ in enumerate(expt_lengths):
+    if len_ / 2 + chunk_lengths[currently_filled_chunk] > estimated_fill:
+      currently_filled_chunk = min(chunk_count - 1, currently_filled_chunk + 1)
+    chunks_indices[currently_filled_chunk].append(len_index)
+    chunk_lengths[currently_filled_chunk] += len_
+  chunked_expts, chunked_refls = [], []
+  for chunk_indices in chunks_indices:
+    chunked_expts.append([expt_paths[i] for i in chunk_indices])
+    chunked_refls.append([refl_paths[i] for i in chunk_indices])
+  return chunked_expts, chunked_refls, chunk_lengths
+
+
+def stripe_pairs(expt_paths, refl_paths, max_size=1000):
+  """Distribute matching expt-refl pairs into stripes with <`max_size` expts"""
+  expt_lengths = [len(ExperimentList.from_file(expt_path, check_format=False))
+                  for expt_path in expt_paths]
+  stripe_count = math.ceil(sum(expt_lengths) / max_size)
+  stripe_indices = [[] for _ in range(stripe_count)]
+  stripe_lengths = [0, ] * stripe_count
+  for len_index, len_ in enumerate(expt_lengths):
+    currently_filled_stripe = stripe_lengths.index(min(stripe_lengths))
+    stripe_indices[currently_filled_stripe].append(len_index)
+    stripe_lengths[currently_filled_stripe] += len_
+  striped_expts, striped_refls = [], []
+  for chunk_indices in stripe_indices:
+    striped_expts.append([expt_paths[i] for i in chunk_indices])
+    striped_refls.append([refl_paths[i] for i in chunk_indices])
+  return striped_expts, striped_refls, stripe_lengths
+
+
 def allocate_chunks(results_dir,
                     trial_no,
                     rgs_selected=None,
@@ -273,7 +318,6 @@ def allocate_chunks(results_dir,
         rgs[rg] = [run]
       else:
         rgs[rg].append(run)
-  batch_chunk_nums_sizes = {}
   batch_contents = {}
   if respect_rungroup_barriers:
     batchable = {rg:{rg:runs} for rg, runs in six.iteritems(rgs)}
@@ -312,35 +356,26 @@ def allocate_chunks(results_dir,
       print("no images found for %s" % batch)
       del batch_contents[batch]
       continue
-    n_chunks = int(math.ceil(n_img/max_size))
-    chunk_size = int(math.ceil(n_img/n_chunks))
-    batch_chunk_nums_sizes[batch] = (n_chunks, chunk_size)
   if len(batch_contents) == 0:
     raise Sorry("no DIALS integration results found.")
   refl_ending += extension
   batch_chunks = {}
-  for batch, num_size_tuple in six.iteritems(batch_chunk_nums_sizes):
-    num, size = num_size_tuple
+  for batch in batchable:
     batch_chunks[batch] = []
     contents = batch_contents[batch]
-    expts = [c for c in contents if c.endswith(expt_ending)]
-    refls = [c for c in contents if c.endswith(refl_ending)]
+    expts = sorted([c for c in contents if c.endswith(expt_ending)])
+    refls = sorted([c for c in contents if c.endswith(refl_ending)])
     expts, refls = match_dials_files(expts, refls, expt_ending, refl_ending)
-    if stripe:
-      for i in range(num):
-        expts_stripe = expts[i::num]
-        refls_stripe = refls[i::num]
-        batch_chunks[batch].append((expts_stripe, refls_stripe))
-      print("striped %d experiments in %s with %d experiments per stripe and %d stripes" % \
-        (len(expts), batch, len(batch_chunks[batch][0][0]), len(batch_chunks[batch])))
-    else:
-      for i in range(num):
-        expts_chunk = expts[i*size:(i+1)*size]
-        refls_chunk = refls[i*size:(i+1)*size]
-        batch_chunks[batch].append((expts_chunk, refls_chunk))
-      print("chunked %d experiments in %s with %d experiments per chunk and %d chunks" % \
-        (len(expts), batch, len(batch_chunks[batch][0][0]), len(batch_chunks[batch])))
-  return batch_chunks
+    pack_func = stripe_pairs if stripe else chunk_pairs
+    expts_packs, refls_packs, pack_lengths = pack_func(expts, refls, max_size)
+    for expts_pack, refls_pack in zip(expts_packs, refls_packs):
+      batch_chunks[batch].append((expts_pack, refls_pack))
+    r = '{} {} experiments from {} files in {} into {} {} with sizes = {}'
+    print(r.format("Striped" if stripe else "Chunked", sum(pack_lengths),
+                   len(expts), batch, len(pack_lengths),
+                   "stripes" if stripe else "chunks", pack_lengths))
+    return batch_chunks
+
 
 def parse_retaining_scope(args, phil_scope=phil_scope):
   if "-c" in args: