Yes, it works for us. We have used it down to low 20s in a tent.

With the nylon bottom zipped (or sewn) to the sleeping bag top it is easy to take up slack in the floor, thereby keeping the upper bag snugly in place over us and on the sides of us.

With down insulation on top and all sides the sleeping pads under us are sufficiently warm for the whole equation to work. The upper bag does have to be large enough to cover the tops and sides of both people, however.

Compressed down under a sleeper doesn't provide much insulation anyway. On an older bag that I used only for me I massaged all of the down under me to the sides of the bag and then sewed the baffles so it couldn't return. No problem. That was 35 years ago and I still use the bag.