Quilts rock at 40, work quite well at 30 to 20F. Can be made to work at zero F, but increasingly less so if you don't have a plan to insulate your head. A beanie is a really piss-poor plan. I apologize for introducing science and physiology into a discussion of staying warm and not dying as it seems to offend you for some reason. I would start discussing alpha and beta receptors in the various great vessels of your body as to why insulating your head, with the same or higher R-factor as the rest of your body, is a smart plan, but I guess I'd be wasting my time. A two ounce hydrophobic down hood really is a waste of pack space and weight. Sorry for suggesting such.
I also apologize for not merely answering your question directly and for adding other information. I do tend to prattle, you'll have to forgive me.
We were required to sleep in the open twice each winter in temps of minus 20 or lower. IIRC, -34 was my record. We used to look forward to it as we actually got to sleep all night for a change. It builds confidence. You should give it a whirl. Try it with just a beanie.