Heres the idea. An A-frame tarp (tube tent without the floor) with a back panel. make it a bit longer for better protection. make it out of a painters tarp and duct tape(sticks surprisingly well!). This is to be used over an air mattress sized 74" x 39" x 8.5" with no side room and some front porch.
Questions for the wise:
1. the mattress will be pretty much up against the rear panel. make the panel wide enough that it can be pitched against the ground here, or integrate the mattress and tape 'em together?
also, height of this? keeping in mind the 8.5" taken up by the mattress.
2. the rear trekking pole, inside or outside?
3. length. in good weather, it will be pitched with a trekking pole at the edge of the tarp on the front end, and the corners can staked directly or tied off at a lower angle. In bad weather, the idea is that the pole can be moved back along the ridge-line so that the edge(where it was) can be staked down. I'll make two tie-outs the same distance back on the edges as well. With a shortened pole, and a long enough tarp, this could go straight to the ground. and a full wall could be made, sound like a good idea? This would we tricky to enter/exit, and would make good hieght at the other end more important.
4. considering the fragile materials, is it worth making a ridge-line? if it had two loops in it and was sandwiched into the duct tape with the plastic sheet it would be simple and the trekking poles could attach there. if the storm pitching was used the front pole could be flipped so the blunt handle end was on the tarp, and the look could be staked down.
also, a guyline idea! Not for this shelter, but I thought of an interesting way to tension guylines from inside the tarp/whatever. It needs grommets.
step 1. tie one end of line to stake.
step 2. thread free end through grommet and then through a cordlock on the inside of the tarp.
step 3. don't get wet tightening your guylines when your sil shelter sags during that rainstorm.
I've got a lot of things on my list, but I have time tomorrow so I might try making one, or in a few months we'll see how it works.