ktm,
I get to save a lot of weight by using curved panels, which add a significant amount of rigidity even before the fabric is added. If the shapes are curved in three dimensions (think egg) rather than two (TD roof) you get even more form rigidity, but the molding of the core gets quite complex.
I'm finally back (again) to working on #2, the 4x10 "hard tent" (she doesn't want a galley), and have the corner fairing finished for the floor-to-ends joints and the wall-to-top joints. The wall-to-top are a tight radius, ca. 1/2", so I'm not trying to wrap the 10 oz. cloth over the edge. Instead I'm using
1-1/2" bias-woven fiberglass seam tape. I also used the same tape and a generous curved fillet of filler on the inside of the wall-to-top joint to make a smooth and strong transition.
If I were building a truck-bed camper I'd probably use 3/4" walls, 3/4" curved cabover or front curve built up from three layers of 1/4" core, and either a 3/4" or 1" roof panel depending on whether or not I was planning on roof storage also. I'd use either a 1" or 1-1/2" deck panel depending on how much rigidity I thought was necessary and how large any open spans are. Laminate layers - one layer of 1200 12 oz. biax for the top and bottom of any horizontal panels, 10 oz. twill or plain weave inside and out for all other surfaces. Generous fillets and 10 oz. plain weave tape for interior joints, 1/2" radii and tape for outside joints.
The above is a significantly stronger laminate schedule and greater core thickness than my trailer, which has done well for ca. 10K miles so far. About half the mileage has been with a 550 lb. interior cargo load, the other half has been "light" at ca. 150-200 lb. load.
I am planning on adding kayak racks on top of the Lite House, so as part of the "make it better tuneup" it's getting a pair of unidirectional carbon interior crossbars at the front and back of the roof to more rigidly tie the roof panel into the walls and direct the load into the rest of the structure. I also learned that if you're going too thin with flat panels you have to brace a positive "bump" into the roof at the fan opening when skinning the outside in order to avoid a puddle around the fan - this too will get fixed soon, and will be properly built into the new one.
Another thing I've learned along the way is that being VERY particular about evenness of panel overhang (i.e., I lay the side panel on the floor and stand the front, rear, and top panels up along the edge of it) is of very critical importance when it comes to fairing the outside curve. I have done smaller projects where this is simple - this is bigger and it's worth as much time as it takes to get the overhang even. If you feel like you need to install little screw blocks on the interior of the curves to maintain the overhang, take the time - even if it means you have to do one side a day instead of two. The other thing that could be simply done is to install small right-angle brackets on the outside surface along the edges of the side panels and screw the top and curves out to meet them.
Back out to trim off the overhanging outside floor skin now! :-)