Cage's buttocks may have some slight issues from sitting at a computer so much.  Hmm.

The buttocks I've tried to insert were derived from the orignal V1 geometries.  I pulled the parts into Wings 3D, selected the edge vertices, inverted the selection, switched from vertex to polygon mode, and used smooth once on the geometry to intensify it.  Then I triangulated all of the unsmoothed verts.  The edges were preserved.

I used TDMT to port all the buttock morphs to the new geometries, then put these intensified deltas into an INJ pose.  The INJ pose was set up to swap the geom, as well.  The main difference between what I did and what you've tested, as far as I can tell, is your inclusion of a figure section.

So the geometries were derivative and the edges were unchanged and the deltas shouldn't have been the problem.

I'll test a few things with the files later tonight.

===========================sigline======================================================

Cage can be an opinionated jerk who posts without thinking.  He apologizes for this.  He's honestly not trying to be a turkeyhead.

Cage had some freebies, compatible with Poser 11 and below.  His Python scripts were saved at archive.org, along with the rest of the Morphography site, where they were hosted.