Redsky, I agree to disagree.
I "think" Lex has done too much "thinking" and it's time to stop thinking and start drilling holes already :)... People will soon stop reading this 10-pages topic. Measure how many panels of what wattage will fit on that roof, and go for it. $200 battery monitor will not generate you any energy.
And, I don't know what controllers with rating 30A or larger have terminals sized for #12 wire. Rogue 30 has #4 terminals, Morningstar 45 has #2 (I think). It could still be necessary to use splices to transition from #4 terminal to a thicker #2 controller-battery cable, but the panel-controller wire in RV systems is rarely thicker than #4.