Okay.  I get it.  The normals check was something planned anyway, to help screen against such problems.  My question about that was, if the normals check rejects a polygon, we can skip the polygon boundary check and move on to the next polygon, correct?

I'm wondering about the polygons region assignments.  As an alternative to edge-checking, what about looping through the polygons in the region, then checking their vertices against the list of vertices in polygons to grab the un-grouped polygons on the region boundary?  That could expand the region by one "band" of polygons.  But that still wouldn't catch an intersecting edge, would it?

Next idea.  Find the centers of polygons and run a "closeness" check on them to place them in the region.

Both are the kind of kludgy workaround approaches that I favor to avoid something intimidating.  :-P

Mixboxes: Okay.  I added the <= condition to the code, and it began to catch everything.

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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.