Before you do that, you're sure the thwarts are sound with the outside tubes, right? I can't imagine CUTTING into my raft! EIIIIOOOOWWWW. But it sounds like a pretty cool plan. I'd just caution though, it would behoove you to enter into this expecting failure. That way, anything that is useful is a success. That is my theory when sewing and other building projects. If the prototype works, flipping cool. But your prototype is your final product.
It sounds like some cool discussions in the upcoming weeks. If this is for the grand, d rings on the inside for the CAFT frame would need to be hell for stout, and gluing can be sketchy. Maybe doubles, 2 d rings to spread the load of LAVA'S WRATH!
All right, it's freaking finally time to go boating!!!!!!!!!!!!!!!!!!