Paco Pads+ Sleep System
So my Fiancee' and I camped out over the weekend...it got to right around freezing...not bad I know, but we were very comfortable and slept well. Here is our tried and true sleep system which we have dialed in over the years. It tends to work really well for us, and has kept us warm down to zero degrees. Take my opinion for that alone, hopefully it adds some insight for your warmth issues.
-Sierra Design 4 Season convertable tent (with footprint underneath)
-Mexican Blanket or other comp. down on the floor of the tent.
-2 inch paco pads.
-Over the pads, we use a fitted twin sheet as an added thin layer...it does a nice job reducing the cold or annoying aspects of PVC...in summer a cotton fitted sheet works, for colder seasons try a flannel or fleece sheet...also, a twin fitted sheet keeps the pads together nicely.
-Brand-Name zero degree synthetic bags...I know many of you love down, and I recognize its superior warmth to weight ratios, but I can't get over the idea of it getting wet and essentially being useless.
-Inside the bags I like to use a 4x4 fleece blanket...you know, one of those cheapie $9.99 things, but it adds a layer of comfort and is great to use by itself when a zero degree is too warm. (also, a silk liner adds some nice comfort without really any space or weight)
-Finally, when it is REALLY cold, I pack another mexican blanket or older fleece blanket to go over the bags...toasty.
Again, just my two cents, but it really works for us, and other than it taking up some space...it is worth it for the comfort factor...I beleive you can sleep warm with a Paco Pad down to the coldest nights with the right additional gear.
Stay warm out there...