AMD is in the midst of correcting their Challenger rear bumper shape. The bumper they sent me had a very noticable crown to it. I called them and am now on the list to receive a replacement bumper when they are available...they said about 60 days or so, and said I could keep the "bad" one they sent me.
So I experimented with straightening the bad bumper. I do some side work as a carpenter. I have lifted large portions of completed houses off floor joist support beams with shims driven in by hand. So thats what I did with the bumper. I clamped a 4x4 to the work table, then clamped the ends of the bumper to the 4x4, and drove shims in between bumper and 4x4 to force the bend out of it.
The finished product is not perfect, I only drove in about 8 equal spaced shims at a time, then removed bumper and check the progress. A continuous row of shims would probably have made a smoother bend, but for a 'driver part' I am pleased with the results. Pics show before and after. A friend is a welding instructor, his comment would be: Its hand made, it's not supposed to be perfect.