Quote - My question that I can't guess at an answer for is why the unimesh is so robust at taking morphs and deformers while all the EF (and pre-curser) figures are so bad at taking morphs and deformers... I love the shape of the P4 figures, and the P5 figures, and the James 6 and Miki 1020 and even Jessie G2 but they just look absurd with the FBMs and fall apart when I try to make morphs for them with magnets. Why are they so brittle? They look much more real than Daz off the rack to me but they just can't morph... not even with the RDNA morph sets. V4 falls somewhere between the EF and the unimesh in brittleness IMO. What makes the difference... it doesn't seem to be mesh density. The only thing I have come up with is the base of the EFs being more ectomorph and the Daz 2 and Daz 3 being more mesomorph but that isn't it either.

Not  just mesh density but polygon flow as well. I'm not familiar much with any of the EF figures because frankly I don't like 'em, but the DAZ figures morph very well due to the poly flow.
I'm not into using the magnets anymore, but if you take a DAZ figure into modo and use the sculpting tools on it with a tablet with pressure sensitivity, you can shape almost anything, evenly, and also do so without ridiculous stretching.