Solar and battery upgrade questions

[ExplodingLemur]

Hiya! We bought a 1900RD last month and I'm looking to get it ready for some off-grid time this summer. I'd like to replace the single 12V battery with a pair of 6V batteries, and add a couple of solar panels.
For the solar side of things, I'm thinking 2-3 Renogy 100W panels, and I'm interested in feedback on roof-mounted vs. portable/freestanding (set up just at camp). Also, where do folks tend to mount their charge controllers?
On the battery front, are there any particular sizes or brands of 6V batteries that are preferred, and where might I find a good double-width battery box to contain them (and attach my battery disconnect switch to)?

Thanks!