Another thing I have done with compound curves is to make a wooden bucks with the curve of where you fold the edge over (female and male bucks). After you have the piece cut out to the proper size, you clamp the metal between the bucks with just the 1 inch edge (which you need to fold over to make the wheel lip edge) sticking out, then you knock this edge over 90' with a body hammer making it flat on the end of the properly shaped wooden buck. If you can figure out what I explained here, you will have a very strong patch panel in a compound curve with a factory looking folded edge in a curved shape not a straight shape. It really isn't that complicated but a bandsaw is needed to properly cut the wooden bucks. You could make this piece in about 1 hour with practice.
Go to your library and rent a book called metal shaping by Ron Fournier. You don't have to read the whole book, but it will show how to do it properly and not get frustrated.

Sheldon