I'm considering doing this hang. I've got a full winter tarp with doors and a walmart blue pad and reflectix type pad. Figure I'd probably need an underquilt but thought I could use my 15 degree down bag as normal and I've got a spare duplicate bag for a family member that I thought I could unzip and use as an overquilt on top of the other bag. I use to do similar for near zero camping in the NC mountains growing up with an army down bag inside a polar tech bag. This was in a tent of course, but it worked well.
Does this sound like it would work? I can definitely test in the back yard prior, but have to get the U/Q first of course.