Doug—I’m not sure if you meant that idea as a way to open up my sleeping bag and use it as a quilt, or as a way to keep my bag from rotating, or something else. (Plus, modding a WM bag seems sacrilegious!)
I’m a tidy sleeper, so I don’t have a problem turning inside the bag without it turning. But then I get no use out of the hood.
As for quilts, I’m such a cold sleeper (6 ft, 150 lb, 61 yo, 97.8F temp with oral thermometer) I just can’t imagine them working for me in the Sierra. Maybe if I lived in Alabama.
So, as an MYOGer, I’m pondering ways to improve sleeping bags.
To save weight: half zipper, no down on the middle bottom (like many quilts).
To have variable girth: nylon gusset on the bottom…with snaps (?) to tighten it up on extra cold nights.
My WM Ultralite bugs me in how damn restricting it is. If I could “let it out” most nights to a somewhat wider width and snug it up on the colder ones, it’d be a really nice feature.