I purchased 2 48"x12"x2" fiberglass waffle boards from(http://www.amgrating.com/
). I plan to use them for an outdoor shower floor, and possible a table top. I may also stow them behind my rear passenger seat in a way that the two create a shelf for storing travel gear.
I also can think of a few times where having a ramp could have been a good thing. Not wanting to get surprised in the field, I rolled up on one with one front tire in my side yard yesterday.
I dont have all the weight of a full-blown SMB but was pleased to see how well they held up here. I figure the span is 38".
After shipping, the 2 costs $200. A bit pricey but Colin at American Grating made the buy easy. At my door front 48 hrs later.