Christ - no worries for the threadjacking.
The cells I got are somewhat flexible - they can be bent much more than the curvature of my roof, but it's pretty flat. They would be fine on your Caravan. I would recommend doing two smaller pieces of plexiglass rather than the one large one I did - more flexibility for expansion/contraction.
Mine is 14V now just because I only had about 48 inches and it worked out that way. (it actually reads about 15V in full sun - more than the cells are rated at)
To charge the battery, 14V will be a trickle charge, but more will make it faster. I'm adding a few more cells on my Kammback in series with my strings on the roof to make them 16V. (will be like 17V short circuit in full sun). On your Caravan, it will be no problem to fit 17-18V, probably 2 18V panels easily.
To the person who asked about the A-B-A testing, no - the panels aren't functioning to aid my FE yet - they will help me recharge when going alternatorless, and I haven't gotten that working yet - I will post a new thread about its success when I make it work.
Update on a bit of a bummer:
Today we had a monsoonish - super thunderstorm. I went out afterward to find an enormous amount of water under my plexiglass. This will be disasterous. I need to figure out how this happened and how to stop it - even if the silicone or a screw was leaking, I don't get how all that water got in there. And it's not condensation - we're talking like a half liter of water. I had a home-made desiccant in there to remove trace vapor, and it's no match for this volume of water... ARGH!
Will post with the problem and my solution!