I've tried:
-Big Agnes Pillow
-REI Travel Pillow (self inflater, bow-tie shaped)
-Horshoe shaped inflatable pillow.
-Sea-to-Summit luxury pillow (2 parts, self-inflating core + soft cover).
-Cocoon Down Pillow
I've matched these with:
-Z-lite sitpad folded in half
-Therm-a-Rest sitpad (orange) folded in half.
-Open-cell foam, one 2" thick with holes for peaches, another about 1" thick. I really wanted this to work as DIY project.
…and various combinations thereof (about 6, IIRC). They were either too wobbly because of the air chambers (no matter how flat I made them), or too hard, or too thick, or too hot, or too slippery, or too bulky, or too fragile, or…
But there was a winner: the Sea-to-Summit self-inflating core (4.9 oz.) with the Cocoon on top (3.0 oz.) (held together with a fabic ribbon). The Cocoon made all the combinations work very well, the hard part was finding a foundation that was height-adjustable, didn't flatten-out, wasn't wobbly, was durable, and easy-to-use. Yup, startling at 8 oz., but this pillow and my BA AC pad aren't luxuries, they're necessities…