You're doing an amazing job! You are definitely saving one that many people would consider too far gone. So much the better when you're done.

I have one question. Hopefully it won't open up a can of worms. Are you using the POR15 self-etching primer (spray) or the brush on stuff?

I had a lot of sheet metal work done on my car including a bunch of rust repair fabrications just like you're doing. The guy who did the work was well regarded pro with about 20 years experience. He does some very high dollar cars including a number of Autorama show winners. Every last millimeter of bare metal got cleaned with skotchbrite, rinsed and wiped, then coated with SEM self-etching primer. The skotchbrite and rinse had to be done within minutes of spraying the primer. He said it was the only way to guarantee it wouldn't rust. Five years later and none of the work he did shows any indications of rust.

I did my front and back bumper mounts/supports myself. I used POR15. I did the front ones before I learned about the SEM, and didn't use it. I did the back the same way he did with the scotchbrite, rinse and SEM before the POR. That was also 5 years ago, and the car has never been caught in anything worse than a light drizzle since. The back still looks 100% perfect, the front is showing a little rust. That just my personal experience. Your results may vary ha ha ha.

Anyhow - here is a big pat on the back for your work and thanks for your time posting it!