What about adding a simple space balnket? 2 bucks. I did this in my hammock last year under my pad and wow what a diff on a cold night! Dont do it on warmer nights you will sweat like crazy. I will never not take a space blanket. When the thermometor dips unexpected, you can add a least ten degree rating to your gear. Best thing is it cost pennies and about 2 ounces!