Improving the wheel opening on '55 quarter patch

I used the Cars panels and used the minimum as Mikey stated. It's my guess that you haven't looked close at the fitment to the rocker mate up and the profile (both being Cars panels - new rockers too). They do not match each other and had to be reworked to mate with each other. The quarter path being the primary part that required rework. I also had some other rework as I used them on a '55 Nomad (remove door jam except for lip that folds into and mated with Nomad door jam - unique to Nomad quarter). At the time I complained to Cars with photographic evidence showing the difference and and was told that I was the first one to complain. They said they would search for a better set and they could not find any in their warehouse, so they provided a 15% refund. I bought quite a bit more and they delivered all to a show so they wanted give me some degree of satisfaction.

Okay - so the bend angle isn't enough and the radius is not quite in the right place.

Here's what I would try: I'd get a short piece of PVC pipe whose outside diameter is equal to or just a bit smaller than the curve of the original sheet metal. You want to fit all the way down in the radius of the curve. Using the PVC as a guide/anvil, bend the patch panel until it eatches the original metal. You could use a body hammer, or try a heavy rubber or plastic head mallet - just see what works.

Once that's right, you'll need to massage the part of the wheel well opening you'll be replacing. It looks like there might be just enough of it left to use as a guide, but not sturdy enough to use as a your dolly/anvil. You'll just have to work carefully to replicate the curves. I recommend getting the outside portions correct first, then getting the fold of the wheel well lip to match up after initial cutting and fitting.