Polygon selections are normally written in the OBJ file(s) that the CR2 file then calls at load time (figureResFile lines).  If you create a custom polygon selection like you're talking about here, you'll find that re-saving the CR2 will write a new OBJ file that contains your new polygon selections, tagged with 'usemtl' descriptors in the OBJ file.  It's never occurred to try to make something like this into a pose file, I'm not completely sure that's possible.

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