Chris, you may wish to look into Sunpower's panels (E and X series). They have single panels upto 435 watts that would fit on the roof of a van. They are certainly not the cheapest around, but I hear you can get "seconds" at quite reasonable prices, though no first hand experience with that.
They provide a much more efficient panel (up to 22.5 percent) by using a different cell structure that makes use of all available light (across the spectrum)
They provide a much more efficient panel (up to 22.5 percent) by using a different cell structure that makes use of all available light (across the spectrum)