Yep, round is stronger than square, but needs must...
Haven't chosen the solar panels yet. That's still a bit out (one step at a time). Whatever I choose (probably 2 each 100 watters) would need to be light and small enough to fit on the limited roof space I'll have. Those SP100s look like they would fit the bill. I'm thinking a 150aH LiFePO battery with 2 100 watt flexible panels (that should keep total electrical weight down to just under 50 lbs). I calculated my electrical needs at between 66 and 104 amps per day, of which 30 amps will be during sun time (refrigerator), so real storage needs are 36 and 74 amps, so 150 ah battery should be more than sufficient (plus I'll be wiring in to the Jeeps electrical system, so I'll be able to charge the batteries while driving, too).
I'm also looking at making the trailer a pop-up using gas struts. Still in the design phase (downloaded Sketchup but haven't had the time to sit down and learn it - most of my drawings are rough in a notebook I keep for this particular activity).