I have added some turrets from GZG. I filled in the hole in the hull with epoxy putty and used magnets on the hull and turrets. I only had 3 turrets so I used one of the TOW units that came with the OG M113s. I had to file down the TOW hatch to get it to sit flush with the hull. For future reference, fill the TOW hatch with epoxy before adding the lid, to allow for more material for the magnet.