My back hurts when sleeping on a select comfort mattress because the air mattress pushes up on my lower back?

Im looking for a way to alter/modify/redesign, or add to this mattress to make it work. I have the sleep number set to lower than 30 just so it wont push up on my lower back. But the problem there is I feel like Im sleeping in a hole. Ive thought about making some sort of spring mattress under neath the foam topper, kinda like those old lawn web chairs. I also have another mattress in between the box spring and air mattress but thats not an issue since I put a 4 x 8 piece of plywood directly underneath the air mattress to eliminate the sag of the other mattress.