Stainless/foam/luan sandwich walls?

Hi all. I'm kinda new here, but have read many threads about building a TD, and the foamie option really appeals to me. (Dream outcome is to tow it behind a Tesla electric car, so light weight and slippery aerodynamics are key.) I don't think I've seen what I'm considering, though - a stainless/foam/luan sandwich wall and roof system. Am I crazy? Is canvas covering really the only way to go?
I was imagining routing a 1"x1" slot in the bottom of the 2" wide foam, and before gluing the wood in, drilling in several holes with T-nuts on the top to bolt the wall down with (and of course, glue isn't out of the question.) And roofing it would be a challenge for sure. I was hoping to get at least 5' wide - does anyone cantilever out over the sides of a (for example) HF 4'x8' trailer?
Lots of questions, interested in your reactions! Thanks in advance -

I was imagining routing a 1"x1" slot in the bottom of the 2" wide foam, and before gluing the wood in, drilling in several holes with T-nuts on the top to bolt the wall down with (and of course, glue isn't out of the question.) And roofing it would be a challenge for sure. I was hoping to get at least 5' wide - does anyone cantilever out over the sides of a (for example) HF 4'x8' trailer?
Lots of questions, interested in your reactions! Thanks in advance -
