Here are a few pics of the bed (still 'beta version' and under construction). I had a folding matress that I started with, (40" x 72"), It was already divided into three 40" x 24" sections, I used an electric knife to cut the middle section where it folds to make the seat backs, and I also cut the rear pad to match the contour of the rear doors. There is alot of storage below the bed, the individual boards below the matress can be re-designed to make the bed longer, the seat taller, etc. The hinges for the folding parts are made from the seatbelts that I removed from the van...stapled to the wood. I also made a strap in the middle, which you pull when folding the seat...very simple design and easy to fold. I will make a few changes later and make the seat backs taller...of course I will have to make longer matress sections too.
The green cooler is used to support the weight on the overhanging section for now. It does work great, but I may put some doors under the bed that would swing open and act as supports. The 'hinged' part of the bed is back far enough that not much extra support is needed on the overhanging part.
When in 'seat mode' the back-rest boards are kept apart at the bottom so they form a triangle and stand on their own,
the strap on the passenger side is used when folding the bed up (more seatbelt material)
Storage under the seat area (always seems to fill up fast) =P
Storage behind seat
Storage under bed...I also cut the side cover for the jack storage area, so that it can still be acessed from below the bed.
I designed this for my personal needs, I dont have kids so did not need to worry about seatbelts of passengers while driving. I have a small business selling art prints, so I made sure that I had enough room to store the 'bankers boxes' under the bed, which turned out to be a comfortable height for the seating. Still working out the rest of the details (curtains, battery, water, etc).