I was about to re-invent the wheel for mine, had a simple system of pulleys and cables all laid out on paper. Then when I went to get hard measurements, I realized my bed would cover my AC... DOH! So I went to the wall. One of the advantages of an 8'6" wide trailer, I can go to the wall with a 12" deep sleeping platform, load my Rhino, and still have walking and tie down room.
As for the system I was working toward. I was going to use cables and pulleys. I figured I'd go to the large rectangle tubing in the corners of my ceiling. That way most of the weight should go down the walls. So 2 eye bolts on both sides in the upper corners. Pulleys on one side and just open eyes on the other. Then rollers on the underside of my bed frame just inside the legs at the head and foot of the frame. Both cables would terminate to one hook, and go through a low pulley to change the direction of the needed force. The driver, which was to be a combo winch (hand/12v power), would be set far about 8' away from the lower pulley to have enough room to pull the bed to the roof. It's less elaborate than it sounds... I think
