So I'm looking to cut gear weight as much as possible and one means I'm thinking of is a packable, hooded, down coat for the upper half of a sleeping bag. I'm always tossing and turning and the darn bag twist with me, also trying to zip it up and down as needed is a pain. I was thinking that I could bring the coat for the upper and cut a sleeping bag in half and use a draw string for the bottom. Is this doable and worth a try?