In reply to johnSD: Exactly. I would if I needed another bag. Sleep in a ball shape, then you can cut two feet off the length of the bag.
Ultralight bags - I have a one season bag, rated to 5C. It's terrible. Packs down to about the size of two fists. I have been cold in it sleeping in my, admittedly quite cold, house. But, I managed ok out in january in it, temps down to about -3C, I was wearing everything, gloves, scarf, jacket, socks, trousers, in it, and slept ok. Put my feet inside the rucsac to keep them warmer and had a decent foam mat. And this was under a tarpaulin, in a tent you would be warmer as no wind blowing across you.