I have the original green regular 72" long NeoAir, which I think weighs 14 oz. From experience, I know that I will be cold using it alone if the air temperature is below 35F. I want to be able to go down to 20F as lightly as possible.

I have several options. I have a RidgeRest shorty which weights about 9 oz and Therm-A-Rest Prolite Plus shorty which weights 17 oz for a total of 26 oz. I think this combination would be plenty warm down to 20F, but they are not full length. Both the RidgeRest shorty and the Prolite Plus shorty are 47" long and I am 6' 1", so they are going to extent only to my knees at the most, depending on if my head is on the pad or not. I could then put my backpack, a Granite Gear Nimbus Meridian, below the pads to insulate my lower legs, but the backpack may not keep my calves and feet warm. This system is heavy, but at least the RidgeRest cannot fail.

I could also put my Regular NeoAir on top of the RidgeRest shorty (with the pack below as above) for a total weight of 23 oz. I'm not sure if this combination would be warm down to 20F.

Or I could bite the bullet and buy a Term-A Rest NeoAir All Season regular 72" long which weighs 19 oz (or the smaller medium All Season 66" long which weights 18 oz-not much difference in weight) Supposedly the All Weather NeoAir would be warm by itself down to 20F, at least that's what I've read on some blogs. That would be the lightest, but most expensive, option for me.

My question is this. Is the NeoAir All Season pad warm by itself, with nothing under it, down to 20F. Does anyone have experience with it?