I used the regular neoair (L) with the 1/8" thinlight underneath in temps down to 17 degrees last year in PA. the ground was very cold, been low temps for weeks. I use the thinlight as a sit pad and to protect my neo air. I can say that when kneeling on the neo air, I could definately feel the cold, very cold, when on parts not over top the thinlight pad. I stayed warm all night using this combo and WM badger, just longjohns.

This year I've been in temps down to 11 degrees with the Xlite and 1/8" thinlight-same sleep system, and stayed very warm and comfortable. Though whatever tactile material is on the bottom of the Xlite grabbed and shredded my thinlight as I tossed in my sleep.