I cut a new hole in both. Thinking about it cutting out the original turret ring would have been a good idea... hehe.. but by the time I cut the hull in half lengthwise it was too late!

I used a halfround file to get it as close to perfect as I can. It's not 100% perfect right now but adequate for it's job. So yes, now I have styrene sitting ontop of the original PnzIII roof.