I'm planning on using a deadblow hammer on top and a dolly from underneath and see how that works out. The metal is stretched so I'm not going to be able to make it perfect and I don't want to distort it anymore than it already is. Even if you just stick the reinforcement plates in and do nothing else it's going to stop any more distortion and more importantly, it will stop cracking.
I'll post my progress here but I'm probably not going to get to it for another couple of weeks....