I finally had time to do some experimenting with the construction techniques for the CarbonMax aft fuselage. The overall idea is that we'd make and sell the skins for the compound-curved forward fuselage and cowling, and builders would make pretty much everything else themselves. That results in a sleek, curvaceous airframe while keeping up-front costs down and maximizing sweat equity in the finished product.
The concept for the aft fuselage is that you cut cradles out of particle board or whatever 3/4" material you have at hand, and use them to enforce the contour at each end of a piece of thin aluminum sheet. Then you constrain the remaining edges of the sheet with straight pieces of aluminum or steel tubing. The result is a clean, smooth ruled surface between the cradles.
You use these assemblies as female molds to make the three aft fuselage skins. For the lower skins, you first make one side, then you reverse the cradles and make the other side. And after that you use the sheet in a different set of cradles to make the upper skin. Actually, you probably make the upper skin first. Anyhow, you use the same piece of aluminum sheet and the same steel rails to make the molds for all three skins
After fabricating each skin, and before demolding it, you create ring stiffeners and longitudinal stiffeners by hot-gluing down 3/4" diameter rods of pool noodle foam and skinning them over with one or two plies of carbon tape.
Here's my test mold. The cradles are a couple of random curves that go a bit beyond 90 degrees. The length is about 26", of which we're using the middle 24". The actual aft fuselage would be more like 84" long, with more substantial side rails to constrain the edges.

The back side of the test mold.

Here I've waxed the test mold and sprayed it with an in-mold primer to control pinholes. The primer here is just Rustoleum gray from the hardware store.
And here we've laid up a test part consisting of three plies of cheap 8oz carbon, 0/90, +/-45, 0/90 and bagged it down with low-dollar consumables.

Next weekend I'll add the stiffeners and break it out of the mold to see how it looks.