Compact: 20″ to 25″ Wedge
This may be the answer. I know that Cracks and Racks cannot put a Rhino basket on this topper iteration, but it seems that it would suit the last journey. I could have a rack that is made for these commercial toppers.
I still have no idea how much they cost compared to the fiberglass toppers. Windows are optional, and I would opt for sliding glass radius windows all around, and a lift window on the back. Then add insulation. (The advice on the web is not firm, but split between solid insulation and spray. All advise to cover the braces, since the aluminum will conduct really well.) The insulation should be done before the beds/shelves built.