I got some time this evening after working on the bike.
I marked and cut out the area I found yesterday. I then applied the old CAD approach and formed the shape of the patch out of cardboard. I cut it out of steel and formed it to match the small local curve at the corner. I cleaned it up and painted it with weld through primer.
Holding it into place with a magnet, I tacked it into place and the welded around the entire seam. There were some spots where penetration wasn't as good so I ran a bead on the backside. With that complete I ground down the welds and smoothed the area out. There is still some high spots, I'll hit those tomorrow and prime it.
I will give it one more good inspection and then it should be ready to take to the painter.