In reply to Basemetal:
Hey
I might find my solution with a bit rope work
1. I have my sleeping liner
2. i use a longer rope to tie the upper 2 corners
3. I sit on the liner
4. I hang the rope onto the arch of my feet
5. adjust the length of rope
the trick is to keep the fabric on my back tight so it can hug my torso quite well
its quite comfortable actually except my feet being cramped by the rope, but some cushioning will make it fine.
I think a longer towel or an oversized t shirt can also do the trick