Hmm.  More complications.  Patching in a new geometry seems to work, until you try to render or activate "show populated".  The altered hair simply doesn't respond, and renders invisible.  So the premise of adding geometry looks like it won't work at all.

I can think of one more possibility.  If the user creates two symmetrical hair groups, build from a mirrored skullcap prop, and styles one side, the styling can be set as a morph target for both sides.  That should result in hair elements which are symetrically styled, but there are potential complications in this, too, primarily connected to the question of whether the polygon orders of the two hair props can be consistently expected to be compatible enough to figure out how to set the morphs correctly for both.

Still working on it.

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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.