Decided to create a new post for this 60 Airsteam based on an earlier post by Larry B who did all the heavy lifting figuring out how to cut the aluminum segments and how to install them.
I've changed the material to 2024 T3 Alclad to match the now stripped interior aluminum skin based on forum advice. He used 5052.
Also have found the ribs of the infrastructure are 1-1/2" thick until the cut off edge of the original fiberglass endcap is reinstalled. At that point and at that interface a 1-3/4" thickness is established. This is a must because without the old fiberglass edge in place you can cannot close the 1/4" gap. And since the other edges of the new panels where they meet the walls and front window have 1-1/2" ribs, the spacer blocks have to be different sizes. I'm starting with 1-3/4" at the ceiling, then 1-5/8" midway, and ending at 1-1/2" at the windows and edges. Hope this makes sense!
Do the newer Airstream's have thicker 1-3/4" ribs?