Just some thoughts as I read these posts.
Seems for you that drag and weight and aerdynamics are huge++++.
I'm thinking a clamshell teardrop shape. Say 2' high at front then taper to 6" in back, about 3' wide and 6' long.
There would be a hinge on the front so the back end lifts up to say 4-5', these sides and back when open would be material. I would probably use rip stop nylon or some sort of tent materials.
You would need 2 poles at the back to keep the back up.
For the walls I would go with foam See the "Foamie" section of the forum.
For the tailer a very simple A shape with the hitch at the top of the A and the wheels at the bar on the A.
The idea of one wheel is possible and does cut your rolling drag in 1/2. I do not know much about these. Perhaps a google search.
The teardropis a very effective shape as the air as it rolls over the front and down the slope actually pushes you forward. It is also easy to make.
A round front end like 1/2 a ball and tapered on all sides to the back is best but harder to do.