I used a cheap pulley system on my HO garage layout for a time in California back in the 70's. Unfortunately, I'm not sure there is enough bracing in the right places in the ceiling of a mobile home for this to work efficiently, so the idea of using adjustable legs might work better. If I was going to attempt this I would integrate the legs with the bedframe for stability like a poster bed, something like this:
http://www.willygoat.com/catal...e.asp?productID=6831
In my scenario, each post would be comprised of three 2x4s. The first 2x4 would be 42" high, the 2nd would be 66" high and the 3rd would be whatever you wanted the final height of the poster bed to be. It could be as low as 4" above the previous level. Then too, I'm not sure a 24" variance for the 2nd level would be enough for some people. Most people are used to 8' ceilings, so I'd try something more like 36", depending on how high 2 people can lift the layout comfortably.
Anyway, these three 2x4's would be sandwiched together to form a sort of ladder at each of the 4 corners. The layout would be a 5x9 sheet of 1/2" plywood (or whatever). It would be on a 1x4 frame with joists just like a traditional table layout. The plywood would be notched at each corner so the bedposts would fit up through the layout. All 4 sandwiches would face out from the headboard.
The layout frame would rest on the 42" level while the layout was in-use. It would then be lifted to the next higher level when the bed was in-use. At each level, a long bolt would go through the frame and post to secure the layout at each corner.
The key is that the layout could be lifted to the next level and then rest on that level until the bolts were secured. I would also secure the posts at the headboard end to the wall. If you do this though, you'd have to put the bots in first and then cover up the lower bolts when not in use as a safety precaution.
