I just dont think the Z actually affects the cam. I've downloaded your models, and they have the same issue I've seen with other versions uploaded. I dont think there is much you can do except make the eyes, mouth and hair 1 sided so they are invisible from the player's perspective, but hair will look funny to others.
While trying to get a Carrie Krueger model in, I realized the Z for the vr cam doesn't really change anything and had to put the cam over her head because of how large it is. Could be the same issue that the pop-chans are just too large headed for the cams to sit proper.