i just tried this a moment ago in MED worked fine

made a simple model. then add a frame (frame2)
move the mesh around break a seam into it. ( i just subdivided a few faces till i made a gap along one area then deleted all the extra faces and verts to cut the mesh open)

now just flatten the mesh out an mdl skin works fine for this now vs grabbing faces

paint it up , relaoded it back in then just delete frame2 if happy with the skin. skin still stays intact for frame 1