You wouldn't have to use a skullcap, but when trying to transfer these morphs, the order of the hair polygons will be important, to be able to be sure of an orderly transfer between the correct hairs.  As far as I can tell, the order of the hair polygons results from the order of the parent object's vertices (possibly polygons - at any rate, the orders of the two seem to be linked).  So it will presumably be important that the base/parent object not only have symmetry, but mirrored symmetry.  Presumably Hiro's head would have this.

I'll have to experiment with this idea, however.  I didn't expect any of the problems with the other things I've tried.  Poser gives its dynamic hair meshes special attention of some sort, which is interfering with any effort to alter them.  That may be true in this case, too.  We'll have to see....

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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.