Finally put a real patch on the hole in the floor of the black Outback out of .040" thick 4130. The hole was much smaller than this but this is how far out I had to go to weld to decent sheet metal. Started with the piece of roofing material as a template and trimmed and hammered from there.
I was surprised how well this repair went. I figured if I got 50% attachment I'd be happy but I'd say it's closer to 90%.
Primered it, painted black too but haven't taken pictures of that. Figure it will at least delay the rusting process, but either way should outlast the rest of the car.
I kept thinking I'm going to be parting this thing out soon but at this point I think what will total it will be some kind of wiring malfunction or fire. So I think slammo is right, probably just keep patching things up as needed until that happens.
While I did this, B and Z swapped out the door lock cylinder, rear door, put on folding mirrors that slammo sent me and a few other things.
I really do need to get started on the billet rear knuckles soon and the Impreza.