Wow, it looks like you have put a lot of thought into what you plan to build. I can relate to your off of the wall ideas. I have found that building a scale model, (one inch to the foot) out of cereal box cardboard, masking tape and glue, really helps. I had to make 8 models before I finally came up with the correct design for my stealth fighter camper. Keeping the rain water out of the trailer is one thing, but even more important is the effect of a hard rain when you are tooling down the interstate at 60 mph. Water will enter everywhere, if it is not properly weatherstripped or somehow protected from water intrusion. Been there, done that. Good luck on your proposed build, take pics of your progress and keep us posted. Keep asking questions, we love to hear them and respond. BTW, if you are interested in building a smaller rig, 40inches wide and 6 ft long, I have some plans I will share with you. I built such a unit that flips up on it's tail and stacks inside the garage against the wall, taking up very little room. It weighs only 245 lbs and works great. :-)

Roly, of So Calif fame. (so to speak)