Yes, in the CR2, keep whatever group is next when you go down the legs from the hip: buttocks for Millennium figures, thighs for Posette et al. You don't need additional welds; that only applies if your OBJ mesh has buttock or thigh groups. I'm suggesting that when you group your shirt, since it's short, you won't need those groups in the mesh. Having the actors in the CR2 will be enough to make it work.