You have to cut the piece a bit larger than the frame and just form and pound the metal over. At the corners you have to cut even closer in a kind of semicircle. If you can get a look at a factory door you'll see how much to leave. You need a big sturdy flat table to work on and when Cam did mine I held one side up a bit so the area he was forming was flat on the table. He mostly used a big ball pean hammer held close to the head to do the pounding. Since the doors aren't flat you have to keep the metal flat on the table. It really goes on well. You have to adjust the door frame angle iron to fit perfectly before you start. I haven't had any experience replacing the inner metal of the doors. When we were done reskinning Cam lined the inner door with the birch plywood right through, then did the framing with 7/8 Maple for the part below the window. The frame below the window was champhered out so the plywood part was even with the metal and quite pleasing to the eye. If you have to do your rad door, do it first to get the hang of it.
