Here is what I have so far...
4x8 HF 1720 trailer, welded and bolted. I also added in a 2x2 steel square tube for both a tongue stiffener and extender, bolted and welded to the 2nd crossmember back and goes 18" beyond the original length.
Way overbuilt my floor being that it is 1/2" ply, 1" wood and blueboard filled interior section, 1/2" ply. All areas are sealed, glued and screwed. Underside is canvas titebond impregnated then covered with 2 coats of Kool Seal. Top side is triple sealed poly using mineral spirits:spar poly at 75:25, then 50:50, then 25:75. Tested in a big rain overnight and what water got into my temporary garage just beaded up. Floor size is 5'4" wide x 9' long.
I've changed my initial design from a teardrop(ish) to more of a semi-standy. Curves front and back. 5' 5" outside width, 10' outside curve to curve length, 5' height. Yeah, I know that once I blew past 4x8 I should look at sizes that equate to a multiple of those type numbers, but I'm weird.

My idea on the walls construction, unless you wonderful folks think I should do something different is as follows...
I'm ripping 1 x 10 pine boards that I picked up as culls, but they are actually beautiful boards into mostly 2" width so they'll be 3/4 x 2 true size. Some, such as ones around door frame, windows and the galley structure support area will be 4 or even 6" wide. Curves will all be done using laminated 1/8 pine, bent to shape. All wood will be fully sealed. These framing members will then be glue laminated to 1/4 ply (maybe I should use 1/8 ?) for exterior. Over that I'll be gluing 3/16" thick by 1.75" wood strips I'll be resawing from dimension lumber. All voids will be fully filled with xps foamboard, laminated to the wood. Inside I want to use 1/8 ply, once again laminated to the wood framing and insulation. So the actual total wall thickness would be 1 5/16, glue-laminated, fully filled with foam and wood.
So, am I building the walls too light, too heavy, or properly? My floor system has an unsupported overhang of 7" on the width and 12" on the rear. I weigh 220 and can jump on the corner without any noticeable flex and can stand with no measurable deflection. Like I said, I way overbuilt it and don't want to repeat on the walls and ceiling, but at the same time I don't want to make it too flimsy either. Any opinions are greatly appreciated and feel free to critique all you want, I like criticism.
Thanks in advance,
dave