Ah! Great information there, although I'll have to use Google Translate. I should have known there would be boostable MPPT controllers. Thanks about the Jill version, definitely a lot more affordable, and more flexible with output voltage. And not so expensive for a solid MPPT controller.

I'm thinking a 100W 18 or 24v panel. 200W flex panels are, well, extremely expensive. I can just do 1 to start with, and the reality is it'd merely be a help, since I'll be burning a LOT of power at night. I wouldn't be surprised if I'll end up using 600-800W a night. I think I might use the solar panel as a 12v charger on a large 80-100A AGM SLA for the main lights, and run the motor and a few chassis lights off of the main lithium batteries. Have a DC-DC Buck from the main lithium pack to run the rest if I wanted to keep running them all, and just bring extra gas for the generator to charge it up both/either during the day. And bring my old Hobby Lobby batteries as backup power for either.