First, I should tell you this concept was borrowed from a great post from 96Delica. I just tweaked his design, as I welded the supports...also made the supports longer and made the platform hinge to transform from bed-mode into bench-mode and vice versa with some ball-lock-pins rather than using carriage bolts and butterfly nuts. Also, my platform is likely longer due to the fact that I have a LWB L400. Platform support rail was cut a bit shorter on the sliding door side so as not to impede that entrace. The platform on that side was also cut at a bit of an angle for the same reason. The bottom of the hinged and carpeted 3/4 plywood platform sits 18" off of the floor, so I could fit a full-size cooler (mine happens to be 17.5" tall), as well as full height rubbermaid bins which are about the same height as my cooler underneath the platform. In order to allow these items to fit underneath, I had to sacrifice a little head room. This isn't a problem when sleeping at all. In bench-mode though, when I sit down (not super upright...the bench back is angled comfortably), the top of my head tucks inside the crystallite window openings just barely below the glass itself. I am 5'9". If you are taller than that and want a bench-mode like this then you might want to consider sacrificing the height of items you fit underneath. Luckily my wife is petite and has no problems at all using the bench. I use it too, but I can also sit on one of the rotated rear-facing 2nd row captain's chairs (for face-to-face conversations in the back for instance. We also fitted a hinged kitchen table that swings down from the rear of the vehicle and secures to the platform using a latch and/or straps. We have a spring-loaded extendable hiking pole (cut) that supports the table very well.
