Thank you all for your kind support and encouragement. Please, if you have a critique or question something I'm doing, please bring it up! I like criticism! It is NOT an insult to me but helps.
The way I'm attaching the walls is kind of like creating a 3-way clamping system. I had a bunch of aluminum angle and square tubing that I cut out of some wonderful, heavy-duty shelves my neighbor didn't want. I mean like over 40 linear feet of the stuff! Including the 18" and 24" wide aluminum sheet used for the shelves.
As can be seen in the photo, I set the walls on the side of the floor sitting on some 1x6, end run pine. This is just to set the location and squaring. For the actual mounting, on the bottom of the floor panel, where the floor overhangs the trailer frame, I've installed 1" square tubing. Over the top of that, at the outer wall side, is 1" angle, 32" long. There are 4 of these pieces, 2 on each side. The interior wall/floor join also gets 1" angle. So, the way it all attaches is the outer angle is first welded to the square tubing. Holes are predrilled in both the tubing and outside wall angle. The square tubing is through-bolted through the floor system. The interior angle is through-bolted down into the square tubing. The outer wall angle is through-bolted into T-nuts built into the floor system. So, the top angle/bottom tubing is through bolted to each other. Outside angle is through-bolted into the floor system. Outside angle is also welded to the square tubing. Oh, and interior angle is through-bolted into T-nuts in the exterior wall.
I'll try to do some photos today, if the weather holds, as I lock the system down.
On the walls, the spars are 3/4" x 1.5". I'm placing them every 8" along the curve, simply to make the bends easier (I think). In 4 positions around the exterior radius will be all-thread rods tying the two walls together at double thick spars. The spars will be held in place by both glue and "L" brackets I've made from that good old aluminum angle I have. Why buy stuff when I can just chop up stuff I have. Yes, it actually pained me to rip those 1x10x12' clear pine boards down into 1.5" spars, but heck I got them from the "cull" bin and they only cost like $3 each and I think I got like 8 spars out of each board. Plus I still have 3 left.
It is nice to actually see my wood/parts pile shrinking. Regina is happy too, since I've actually been throwing stuff away as I've continued in the build.
dave