OK, I have been spending way too much time thinking on this... I'll try to upload some of my hand sketches to show what I'm up against.
(I've been sketching in a memo notebook, and I didn't bother with a scale.)
The gross exterior dimensions I've come up with so far:
51 1/4" Wide x 76 1/4" long, by 18" tall
Those numbers came from topview1:
and the side view:
and the tail view:
SO... envision a plywood box sitting on a flat deck. The front 2 feet is an open deck with expanded metal, surrounded by stake sides. The back 6 feet is an enclosed box where the top hinges open at the sides, creating two tables running the length of the box. These tables when open, will support the coleman stove, etc. When closed, the (4) bikes are mounted using front wheel fork mounts. I'm thinking of using PVC as the "trays" to align the bikes. 2 bikes face forward, 2 bikes face backward, to minimize handle bar collision.
So - that's what I've come up with.
The hitch on the car is not included in my "budget."