My $.02 worth
I too have done alot of homework/napkin drawings/head scraching & acctually started this very project!
II started with an old drop center hotrod axel that happened to be 5 on 4 1/2bolt pattern, flipped it, welded new perches on, & with 35's I get 20" under the center of the axel & 28" to frame
I also think 4'X6' is the optimal size for a tow behind. I am going with a single flip design with angled poles back to the frame (set up is allways the same) & jacks on each corner.
Due to cost issues I plan to use my existimg 6'X7' spring bar style dome tent, it is easy to setup & take down & cheap to replace or repair
I'm still working on the trailer at the moment, but some of the design features are, fresh water tank w/pump,12 v fridge, battery box, porta-pot, 12 v lighting & maybe some other stuff! We'll see!:greg:
There some good ideas in here, good luck, & keep the faith!