diff --git a/mrdna/readers/__init__.py b/mrdna/readers/__init__.py
index 8a6110c1feacbfde8c82d835f67e15c9f701f63b..e430d876c2cbd037f6c6f53162f6b929e6b70a60 100644
--- a/mrdna/readers/__init__.py
+++ b/mrdna/readers/__init__.py
@@ -20,6 +20,8 @@ def read_cadnano(json_file, **model_parameters):
 def read_vhelix(maya_file, **model_parameters):
     data = parse_maya_file(maya_file)
     segments, dsSegmentDict = convert_maya_to_segments( data )
+    if 'dimensions' not in model_parameters:
+        model_parameters['dimensions']=(5000,5000,5000)
     model = SegmentModel( segments,**model_parameters )
     model.set_sequence(m13seq*10)
     return model
diff --git a/mrdna/readers/polygon_mesh.py b/mrdna/readers/polygon_mesh.py
index 2ab0a00043dc777b4684ff1122369b02c6c064bb..4e2027c63ac5cedb09bb5a70ffcaf638f92151e9 100644
--- a/mrdna/readers/polygon_mesh.py
+++ b/mrdna/readers/polygon_mesh.py
@@ -314,10 +314,8 @@ def convert_maya_to_segments(helices):
         nt = 0
         def add_primes(b,nt,fwd):
             if b.end3 is None:
-                if not fwd: print("3prime at {}[{},{}]".format(hn,nt,fwd))
                 segments[hn].add_3prime(nt,fwd)
             if b.end5 is None:
-                if not fwd: print("5prime at {}[{},{}]".format(hn,nt,fwd))
                 segments[hn].add_5prime(nt,fwd)
 
         for b in ordered_fwd_bases:
diff --git a/mrdna/segmentmodel.py b/mrdna/segmentmodel.py
index 7c7b47df5d0da22d4f53b31ddc24f5a7963b9d3e..b2b4ef8115e9ffcd0cfeb46d7255f621b468c96b 100644
--- a/mrdna/segmentmodel.py
+++ b/mrdna/segmentmodel.py
@@ -905,6 +905,7 @@ class DoubleStrandedSegment(Segment):
 
     ## Real work
     def _connect_ends(self, end1, end2, type_, force_connection):
+        debug = False
         ## TODO remove self?
         ## validate the input
         for end in (end1, end2):
@@ -914,10 +915,10 @@ class DoubleStrandedSegment(Segment):
 
         ## Remove other connections involving these points
         if end1.connection is not None:
-            print("WARNING: reconnecting {}".format(end1))
+            if debug: print("WARNING: reconnecting {}".format(end1))
             end1.connection.delete()
         if end2.connection is not None:
-            print("WARNING: reconnecting {}".format(end2))
+            if debug: print("WARNING: reconnecting {}".format(end2))
             end2.connection.delete()
 
         ## Create and add connection
@@ -1133,12 +1134,14 @@ class Strand(Group):
         self.children = self.strand_segments = []
         self.segname = segname
         self.is_circular = is_circular
+        self.debug = False
 
     ## TODO disambiguate names of functions
     def add_dna(self, segment, start, end, is_fwd):
         """ start/end are given as nt """
         if np.abs(start-end) <= 0.9:
-            print( "WARNING: segment constructed with a very small number of nts ({})".format(np.abs(start-end)) )
+            if self.debug:
+                print( "WARNING: segment constructed with a very small number of nts ({})".format(np.abs(start-end)) )
             # import pdb
             # pdb.set_trace()
         for s in self.strand_segments: