Sinbad, I doubt that a hair dryer would get hot enough or it would also burn your head when you used it. I would take a piece of wood, lay it across the case, put weight (cinder blocks? bricks? weight plates from your gym room?) on each side that is warped upward, and use the heat gun to warm it just like you thought. Walking around the case constantly so you don't melt it.... Or is you can do it long term, put it back in the hot shed laying flat and face down for a few years and let the heat warp it again in the other direction.