I have a 2 x 10 that runs along the drivers side from 4inches back behind the drivers seat to the back corner of the van right against the wheel well. I build a box that sits in the step well for the side doors that is as tall as the top of the 2x10. I then ripped a 34 in 4x8 sheet of plywood and put a piano hinge on it so that it folds in half. I then laid the plywood over the 2 x 10 and the box, no issues with support. I use a inflatabke full size twin air matteress. When i have to get 2 skids in, all i do is lift the edge of the plywood and fold it uo. I have a eyelet screwed into on the underside of the board and i use a short bunge strap and hook it to the eyelet and to the 1st rib back fron the factory headliner on the interior roof. I have had no problems with 2 skids in this fashion.
Now if i have to sleep while the board is folded, i use a smaller air materess and deal with that. no big deal. If for some reason i need more room i can either folld the board completely in half and lay if flat and i can also tip it up and stand it on edge behind the drivers seat in that 4 inch area that i didn't cover with the 2x10. then i have the complete load floor. i haven't had to do that yet at all. And i really don't expect to.
The area behind that 2 x10 is great for storing a case of water until i need it in the frig, food before it gets in the micro wave, straps, chain, gloves fuel cannisters for the big buddy and the butane burner, gym bag full of clean clotes, dirty clothes bag and toiletries other stuff.
Oh I also use a heavy shower curtain rod and hung a heavy quilt over it and used nylon ties to hold it folded in place and use that as a seperater from the cargo area, Using the shower curtain rod lets me take it completely down or move it anywhere i need it using the holes in the side wall and roof supports. I insulated the 4 ft area i sleep in with Dow blue foam board and the same air bubble insulation that Jack used, covering the side wall, ceiling and side doors. My only issue is i used duct tape to hold the bubble insulation in place, bad idea! I need to fix that and then cover it all with wood.