The shop has my sketch but check the below link and you'll see one real close to what I'm doing. It's the third row down and on the far right. Thier room is attached to the tear via an awning rail. A 1/4" solid plastic coard is sewn into the matl at the tear and just slides in the awning rail slot. That's one way. I'm using snaps that screw into my edge molding (roof side) at existing screw holes. I've got eight snaps across a 5' stretch. Sure it's not air & water tight but it works fine for me. If it looks like I'm going to be camping in the rain, I'll just take the Dalton.
Neat Idea Gage. I had the same idea sometime back. Just have not gotten to that point yet. When you get the setup. Please post a few pic's of how it was all done. How are you going to store the setup?