I don't think I can add anything significant, other than I've had odd experiences when using displacement-map methods on figures. Every Poser human I've tried, from Posette to Aiko 3, will only accept a very slight dioplacement before polygons seem to vanish from the mesh, leaving those little patterns of black holes in the surface. On reflection, the mention of Firefly rounding errors could be part of the problem. The effect does seem to be worse on the newer figures, which have the smaller polygons. Aiko 3, currently free from Daz, is the only one of their hi-polygon unimesh figures I have.