Quote - Morphs are near impossible, there's simply not enough polygons in that area

That's definitively the problem: u can't even cut inside the mesh to bridge some other vertices to the original geometry, a trick that can be done to add genitals to M4 without adding a new figure.

The sole solution is to cut a part of the mesh, losing the welding of the hip to the others parts ( right and left thighs) in the original mesh (but not of course inside poser), then importing a "foreign" part into blMilMan_m4b.obj. I have taken  a part of the hip of the Appolo Maximus geometry, then welded this part to the remaining hip and thighs.