markskor wrote:Isn't a quilt with a toe-box zipper, still a sleeping bag?
That's what I was going to suggest, Goldilocks.
A #3 zipper to knee height with a single zipper pull would by itself add about 1/4 ounce to a bag/quilt/thing. A #5 zipper would be double that. And a down filled draft tube running along side might add 1/8 ounce or so, or somewhat more if you insisted on a stiffener there. Some of the small cottage bag/quilt makers will do custom mods like this.