Hi, In the past I've seen the sheet wood for the fuse warp because of humidity while I'm building the wings etc. and the fuse. parts are sitting in the box being exposed to the air for a few days. This is especially true with kits made in different parts of the country or world where the humidity is vastly different than where you're at. (My funiture factory owner friend explained this to me) They almost always warp in the same direction resulting in a 'banana' curve to the fuse that's almost impossible to get squared. I've found though if you soak em' with rubbing alcohol or ammonia water mix and then weigh them down on a flat surface and letting dry before assembling the warp will come out, it might take a few 'treatments' to achive the desired outcome. Be sure they are really dry or the warp will return.
Rick.