Thank you for creating an account on Hunt Talk! We require that all new users contribute at least 10 posts before gaining the ability to start new threads. Once you have made 10 posts, you will be able to start new threads in the forum.
Just a straight air mattress insulates less than a foam one. I use a Big Agnes sleeping bag with the Air Core pad (just a small air mattress w/o foam) till about 32ºF then add a 1/4" foam pad underneath it till about 10ºF. That's about as cold as this bag will go.
1 pointer is right, you need an insulating material of some kind between you and the groung. I use a 1 1/2" self infalting pad w/a closed cell pad under that. Nothing worse that a cold miserable night's sleep.