When I was building my hardtail on my jig last December, the bottom rails were not the same level. No problem, I just fired up the map gas torch, heated everything up and hammered like hell. It was only after it cooled that I realized I had also bent the ready rod that was supposed to be holding everything perfectly inline for the engine to pop right back in. I sure felt like a chimp that time. It took a bottle jack and very careful measuring to get everything back where it was supposed to be.
Peace & Grease, Dennis