SDcamper, a rubber sheet or heavy plastic tarp would work, but it would not support the styrofoam. And a hole in the floor won't do me much good, since we so rarely heat the inside of the trailer (especially while on the road). I am going to install some heat tape or tank pads, for use when we have hookups.
kevden, I like the idea of unistrut -- very beefy stuff! That'll hold up the corplast and the foam, for sure.
I'm still trying to get a flat smooth bottom, rather than one that sags. So I am hoping to extend the beams in a downward direction.
