Didn't take measurements or bring the laptop with me. What I have in mind for the wheel tubs is to build them like a drawer. Nothing special for tracks. Probably just some tubing sized for high strength telescopic action. I got to thinking that slide-out wheel tubs would be perfect for easy access to those areas underneath the floor and double as a quick shelter if I want one while wrenching at the wheels for storm protection or shade. Of course, I need to think of a substantial locking/latching mechanism that wouldn't let go while running down the highway and also too much work for the average Joe to break into.
Originally, I thought I would build the tubs from plates that could be unbolted for access. One-piece drawers would be far better. Making them leak-proof might be the hardest.