After getting the B-pillars fixed, I revisited the roof skin. I must've warped it slightly when repairing it (despite being careful not to), and/or just not gotten the curve of the back edge quite right. When test fitting it, there was some oil canning, I suspect caused by shrinking. I have spent significant time/effort getting it mostly back to looking right when clamped down. Thankfully I think I have it well within range of a body filler skim coat, which I was planning on eventually doing anyways.
Additionally, as can be seen in these pictures from when I took the roof off earlier this year, there was some factory installed closed cell foam rubber (neoprene?) inside the roof. I assume this is to help support the otherwise unsupported outer roof skin and minimize any oil canning.
One note, my gut instinct would normally be concern for this foam holding moisture and causing rust, but the spots where the foam sat were actually the only spots that didn't have any surface rust. So I think the closed cell foam, and the fact that moisture really shouldn't get in there, makes it a non-issue.
This foam got relatively torn up when I removed it, and it was visibly compressed (permanently) from what appeared to be its original thickness. I found some seemingly identical neoprene foam on Amazon. I got slightly larger (12"x12") than the original (about 5"x10"), in 3/4" thickness. The pack came with 4 of these pieces, but I am currently thinking I will only use 2.
I also am thinking I will line both the inner and outer roof skins (both on the inside of the roof cavity, and not visible once the roof skin is back on) with Kilmat insulation. My thought is that it will add a little insulation and vibration deadening as a might-as-well while I'm in there, and also on the outer skin help stiffen it up a little bit and maybe further prevent any oil canning. And maybe even protect the sheet metal a little, but I'm not relying on that (I will be painting it of course).
That brings me up to date, I test fit the roof skin with 2 layers of Kilmat and a layer of foam in roughly the spots I am planning on. I have maybe a couple more minor tweaks to the skin itself, but it's basically ready. And the foam/Kilmat seems to fit very well, and also support the roof skin very well. It is surprisingly solid feeling compared to how it feels when there is no foam.
Anyways, I'm mostly just journaling and thinking out loud here. Massaging the sheetmetal is painfully time consuming. But I'm learning a lot and slowing moving things forward every day.