I'm a noob - but I've been napping in the basement in my HH. Yesterday I took my 30* bag in with me, and got into it as well as I could...my left should was out of the bag....no big deal I thought.
After a couple hours of napping I realized that my left should was really cold.
So today I procured some shock cord and some other small cordage from the local climbing/backpacking store and strung up a down blanket we had laying around.
I used some tarp clips to attach the shock cord to the blanket (this is of course just for experimenting), attached the shock cord to an accessory line (tarp line) using some prussics and nacribiners (also learned o make them today!).
I crawled in after a few adjustments....I couldn't believe the difference. I had a small fleece blanket on top....no sleeping bag.
Soooooo I'll by looking into making an underquilt now.....