Geometry switching is the accepted way of altering which mesh is displayed for an actor in Poser. You could, for instance, swap between two different obj files that just happened to have the exact same vertex and facet definitions, but have the V coordinate of the texture inverted (V' = 1.0 - V, with appropriate variations if UDIM is in effect. Ask if explanation required), thus giving the same effect that changing the VScale input of the image_map node from 1 to -1, as suggested above (much simpler to achieve).

Several folks, including my humble self, have python scripts capable of reading, modifying and saving obj files to overcome limitations of Poser's Python API methods for dealing with geometry. (Still no way to create new facet groups outside the UI. Better be there in P12 or consequences ).

References to free UVMapper are PC/Windows only at this point. UVX for macOS is a PowerPC/Fat binary and no longer executes on modern macOS since the retirement of Rosetta.

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