Thank you guys for the welcome, as well as the vote of confidence!
I have been reading here (and solar forums) for quite awhile, but I still have years of threads to go through - I love learning about and seeing what others have dreamt into existence! I am in Florida, for what it's worth - we basically do not have a cold season, and for much of the year, it is hot and humid all day AND all night. Add that to being old and creaky (I now require a mattress and cool temps to sleep comfortably) and we need a trailer if we want to camp frequently.
I keep coming back to foamies - they show up in searches whenever talking about larger than average homebuilt trailers - but I haven't quite convinced myself that they're as strong as they obviously are. Right now, I'm leaning towards PMF over plywood sandwich panels, but that's partly because it plays to the 'cheap kids' playhouse' kind of skills that I have to my name. Unfortunately, on the ground, I can overbuild to my heart's content. When weight and motion are factors, I feel very out of my element.
Honestly, my problem right now is wondering if I should even tackle this. I saw a customizable trailer manufacturer that can build a 7'x14'x6'tall single axle enclosed trailer for around $3k base. That's big enough to mount four 400w solar panels on top!! I'm not sure how much extra it would be to have them beef up the design to accommodate the panels and the mini split components, plus any other upgrades I'd want like brakes, but it's an attractive option. Not actually aesthetically attractive, of course, but we couldn't care less what it looks like if it meets our needs well. If we do build, my plan is/was to build taller versions of the builds pictured in the second and fourth posts in this thread:
http://tnttt.com/viewtopic.php?f=2&t=65778 . Part of me would be very interested in paying a good bit of money for a 7'x14' open trailer and building on that, but I'm not sure I'd be capable of building something both sturdy enough and light enough.
Anyway, I'm still enjoying soaking it all up! You guys have so much collective knowledge here!