Consider doing the framing in aluminum. Then determine if you want to screw/bolt it together, or weld it together. My TT (2010 Crossroads) has a 6 sided structural frame/cage that is screwed together. Supposedly lets it move. Crossroads subsequently moved to a welded frame. (The "frame" is steel of course).
By building it from frame up, you can control the insulation R value, accessibility to components, whether or not to use a rubber roof (or other material) etc.
You can also control/plan for aerodynamics, especially on the nose.
I think this will be a very cool project and worthy of a blog, and or an extensive DIY thread, or even a submission to a RV dedicated magazine. Keep extensive photos and records of your progess.
Please keep everyone up to date.
