The RR 20X24 uses carbon fiber tubes. I would post a photo of the bed but am traveling and can not at this time. Even so, it is fairly complicated visually and I am not sure it would be easy to understand even with a good picture.
If I were to build a 20X24 camera again I would strongly consider the modular approach taken by Kerry Thalmann. I think the mono-rail design would be easier to assemble for most persons than a traditional wood bed design.
Yes, it would be nice to be able to put the "bed" or rail part of the camera on the tripod and then attach the back etc.