I don't think that R value is all that important. Sure some insulation is good but that doesn't mean that more is better.
I'd have to disagree; my older Neoairs were good to about freezing or so, my Xtherm is comfortable to zero- 3.2 vs 7 r value
if you're going to be carrying an additional ccf pad, then obviously you've just increased the r value and it will be comfortable to a lower temp- the r values are additive, so a 3.2 (Neoair) inflatable used with say a z rest ccf pad (2.0) gives you a r value for over 5 making that combo comfortable below freezing
what you have underneath you is almost as important as what you have on top of you in my experience
