To delete the vertices, you'd have to spawn a new geometry in PoserPython, which can be a bit complex, if you want to retain the UV and materials data.  You'd have to identify the parts you don't want and leave those out of the new geometry.  Then you'd have to build the new prop using the PPy geometry handling API, using specially formatted Numeric arrays.  It might or might not be easier to work directly with the OBJ file, presumably outside of Poser.

The next easiest approach after flattening the base would be to assign a new transparent material to the unwanted portions, I think.  That would involve identifying the polygons you don't want and assigning them to a new material which is set up as transparent.

===========================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.