I came across a length of lycra/polyester in the clearance section of a local crafts store today. I immediately thought of grabbing it to make a sleeping bag liner out of - however, there wasn't a full 2 yards left on the roll. I took all they had, figuring with the stretch factor of the fabric, and geometry, I could make something work with the fabric. If not, then I'm only out about $5.

The piece is ~62"x~62". If I'm standing on my tip-toes and hold the length in front of me, with it just touching the ground at the bottom (simulating sleeping with feet fully extended), the top comes a bit below my shoulders.

Now, I know that the fabric will stretch, and I also don't need it long enough to put over my head, so this may be a good length to work with. Here are a few ideas I have to try to make this work with what I have.

1) Add some kind of elastic to the open end of the liner, where I can pull it up over my shoulders and it won't just pull itself down, but also not so tight that it'll cause any problem with my throat.
2) Use the diagonal of the fabric to serve as the length and try to figure out a way to fold pieces together/sew it together to make it work.

I can't logically think of a way to make 2 work, so I'm leaning more towards 1 (since it's also something I can add in afterwards if I decide that it's a bit too small for me).

Any input?