OP, unless I'm missing something, you are planning a system without having done the energy audit. What is your estimate of daily AH draw according to Excel spreadsheet calculator? It calculates the array size automatically - how may watts was suggested?
It might be that you only need flat 350 or 400W. Then you won't have to invent foldable multipanel contraptions on the roof, or mess with a supplemental portable panel. Camping should be fun, not a hard work. Fixed roof mount is the easiest to install and use. Make it tilt-able so that you "could" climb the roof when you feel like, and when you don't feel like - it would work flat as well. This is as far as I would go - roof mount with tilt option. Max array size.