HA HA IT WORKS!
I too have been trying to figure this out and was doing the hr2 thing, but losing the morphs.
Until I tried loading the flipped obj as a morph target and everything works fine, the morphs and mat files still work a treat. Using Koz's long hair that is, i'm not sure of others yet, Sanfran hair is one that I always wanted to flip, so i'm going to try that now.
Cheers
Kev.