I consider my Warmlight Down Airmattress to be an integral part of my camping gear and it goes with me all year round. Its wider at the shoulders and tapered towards the feet and about 3 inches thick and ok for camping on snow especially with a thin closed cell pad under it. I think its 80 inches long. I can put my foam pillow on top of the pad and have lots of room to stretch out and have my toes still not hanging over the edge. The only thing about such a thick pad is you will want to put spare clothing items etc closely around you to insulate the floor and give your arms someplace to land if you stretch them outside your sleeping bag.

It weighs 27 ounces.

I can float on a cold lake and be in an insulated space - it floats quite high.

When I was a kid I was thrilled to get a 3/8" blue foam pad when they first came oout - it sure beat sleeping on the ground, but it probably weighed 10 ounces. For 17 ounces more I can have a large 3" thick pad.

When trying to go lighter, you do not have to give up everything comfortable - leave out some other junk instead. I have friends who are real minimalists - one carries a machete and bivy sack, the other carries a sleeping bag. Neither has a pad nor a pack. I guess they carry food and water in a shopping bag and about the only hardware they have is a lighter. Thats all they take. Who cares how heavy their sleeping pads might be if thats the primary piece of camping gear? Like a pad, bivy sack and coat, and carry it all in the bivy sack.
Jim