Ray Jardine's quilt kit contains what he calls a "draftstopper, " which I gather is just a strip of shell material along each side that can be tucked under to prevent drafts. Might be worth considering.

My experiments using a light sleeping bag as a quilt seem to indicate that it's maybe not for me. I always wound up zipping it closed before the night was over. Also, my bald head requires more insulation than a stocking cap.

It seems as though if you make the quilt wide enough to tuck very far under you, you've essentially made a sleeping bag and only saved the weight of the zipper and maybe the hood, although personally I would want the quilt long enough to pull up over my head.

I did make a prototype synthetic quilt similar to Ray Jardine's concept, using materials I had on hand (light nylon taffeta and a single layer of Climashield, which has since lost about half its loft.) I used Jardine's idea of sections of yarn to stabilize the insulation and incorporated his "gorget," which contours the quilt over the chest and shoulder area, a feature I would definitely use again if making another quilt. No footbox, just sewed the end closed and sewed up maybe 18" to make a pocket for my feet. Although I wouldn't use it backpacking except in the warmest climate, it's been very useful at home for taking a nap.
_________________________
Always remember that you are absolutely unique, just like everybody else. -Margaret Mead