If you're only going to run it 4-cell and know someone with a mill just have 'em buzz the fins off. OR...if you've got a lot of spare time and a Dremel... Mind your fingies though as it'll get HOT while you're grinding.

You need the "plate" that's left though as it is potted to the electrical bits inside and seals the crap out. Won't be enough cooling for 6-cell use after that though.