If I had to do it again I would have bought that rear pan from AMD and cut the corners out of that pan and butt welded them into my car. Would have been far faster easier then what I did.
I don't have any special tools to form/bend metal other then that Dimple Die and a vice. So you can form the steel patch in a vice using cardboard templates to get the shape. It has a pretty complex shape but I brute forced it kept bending it tweaking the shape till I got it to fit. Then once have fit you want hammer dolly to smooth the metal out.