Thanks for the help
I think I figured out a good system based on both of your ideas and absolute cheepness. I used an old bed frame (free). With the frame adjusted to double, or full size, and the head board connectors chopped off, it fits perfectly in the back of a full size truck. For the legs I bolted on some tube steel that slide up and down so I don't have to commit to one elevation. At the highest poit I can get a cooler underneath and at the lowest point I can sit up in the topper. Because the frame came with a cross piece, the plywood can be cut into quarters for access panels.
The end result is a fully adjustable, lightweight, accessable, easily removable, and cheep (without the plywood the whole thing cost about $8.00) system. The frame also collapses for easy storage.
The minivan is a good Idea, but I am tired of being the weak link in the shuttle. I've paid my dues off roading in a Neon. Although the challenge was fun, constantly replacing the gass tank and oil pan was getting exspensive. And it also went to the chrystal gorge.