Speck Lover, that night that you and your daughter got too cold would have been a lot more pleasant with just the undercover system. I can sleep comfortably in my hammock with just the undercover and no pad down into the upper 40s (I have a 19 degree Western Mountaineering down bag). You get down into the lower 40s and you need the undercover + the pad. I hope that helps!
Thanks for the information Carlito, I figured there had to be a better way. My daughter and our frozen azzes thank you too.