Many of the build resource sites and videos we found focused primarily on conversions that accommodated 2 people and finding insight on a 4 person sleeper was quite a challenge. What we did find usually relied on a ~$2K lift system that we felt would take up too much space and frankly, we didn't feel like it was worth the investment. Our original plan was to suspend a modified Ikea frame from the ceiling leveraging nylon straps and the OEM rings that could be raised and lowered. After building it out and a a test install, we decided to scrap the plan and go back to the drawing board. The new plan consists of 4 low profile extruded aluminum bars mounted to the walls with accommodating L brackets that can be manually raised and lowered. Brakes on the brackets hold them in place.
The key to this design were these telescoping beams (below) that we found at Ikea for ~$10 a piece. This allows the bed to raise and lower with the contour of the Van (It is narrower at the top) The beams are attached to 2x4s via hardware that came with them.
We threw a piece of plywood and a bunch of sandbags to test out the weight before we had the lil ones climb up there. No issues at 150lbs. I even climbed up there myself.
Finished the 2x4s with the same stain as the ceiling.
Upper mattress is 4" memory foam
Sits on 1/8" plywood and trimmed with ceiling planks (update soon)
More to come...