BBZ,
As Wuck suggested, the place I got my siding from (The Metal Company -Arvada, CO) has the ability to seam two pieces of their aluminum material together like the original FWC. I couldn’t tell you if they would guarantee it to be watertight, but my guess is yes. The aluminum material is on a big role and is, I think, 48” wide, so even with a Mesa design, they can get 82” width plus, and can make it whatever length you need. Cost is the limiting factor, at least for me. I decided I would try to use what I had, and just cleaned it off good, primed it and put a good coat of Rustolium White on it, and live with the hail pock marks. I had one spider crack that got covered up, and as Shellback did, I used larger size #10 screws with neoprene washers. Then sealed with RV sealant. It’s been good for two years now.
Poky