Richard, thank you for all the data you provide. This thread plus the recent ones on down jackets are really helpful in getting a couple sticking points in my winter gear list cleared up.
My winter sleeping pad system is one I've been trying to figure out. Last winter in the Sierra's, used a Thermarest Z-Lite (r-value 2.2) on top of a 3/8" blue CCF from REI (r-value 1.35, if my math is right). Now I understand why I why still chilly in my 15 degree bag.
This winter, I was originally considering an insulated pad, but am having trouble justifying the expense for something I'll use for maybe 3-4 trips a year.
I have a NeoAir short. If the manufacturer's claimed R-Value of 2.5 is accurate, I might be okay with a system of the Z-Lite underneath it and my GG 1/8" Thinlite (r-value .45) on top for a cumulative r-value of 5.15.
I'm hoping this works as I'd rather used what I already have, and the total weight is ~23 oz, lighter than an Exped Downmat, and I'd need to bring the CCF for sitting anyways(And as an emergency backup in case of a leak).