If I was doing it I'd think I'd fit the sandal to the toe, with a ghost part (or bone, if you will) working the other way (back tward the foot) to bend only in "down" (where otherwise the sandal would go through the foot) Ingenue Vickie's sandals have a "loose" morphs, per the pic, incidently but it is just manual FBM (it also has to do the strap). Could be hooked up to ERC, though.