there was another BPL post I cannot find, that discussed combining two pads does not necessarily equal the combined R value.
example: foam pad 2.6 + air pad 2.2 does not have to equal R value = 4.8
if the foam pad is on top, air pad on bottom, better R-value.
if the air pad is on top, then you will get colder lower combo R-value, because air is a poor insulator.
your experience may be different, but it's something to consider.
I prefer the 2 foam (no air) pads method, because of the versatility, you will have to rig something to keep the two pads from slipping. but that's another thread (hint: velcro)
Air expands when hot and shrinks when cold. You can fully inflate an air pad, but at 3AM, the air padding will change.