Here's a bag I tweaked last year.
gargsleepbag 021.JPG

Added some grosgrain loops to the bag and suspended with some shockcord. Placed the bag zipper up for easy exit/entry. With a vest slid down over my noggin'.

gargoyle sleep mod 060.JPG
Chopped a hole in the end for the hammock to slide thru.

gargoyle sleep mod 066.JPG
Good pic of the hole.
If I had to do it over, I'd seperate the seam of the footbox at the lowest point. That way it would fill the gap better (all theory)