New question:
Is there any reason the galley NEEDS the plywood skin in between the wooden frame and the aluminum skin? Seems to me that the spars could be used for mounting things like lights/handles/etc, and you could bond the aluminum (perhaps in 0.063 or 0.080) to the frame with, say, 3M 5200, and use clamps and perhaps a few screws to keep it in place while curing. The rear of the trailer won't see any real aero loads or road debris, and assuming the wooden frame is where all of the stiffness is coming from anyway, the wood skin feels kind of redundant. Unless I'm missing something obvious, which is definitely possible, but I like deleting the challenge of bending the wood to that contour... Thoughts?