Is the thin bottomside an issue? I realize...
Is the thin bottomside an issue? I realize that you must have a sleeping pad, which I do, but the pad is a 1" Therm-a-rest. Also is the extra weight of this bag worth it?
The thin bottom isn't an issue. By putting your weight on the bottom in a standard bag, and crushing down the loft, you're rendering the insulation ineffective. A trick I've always done in simply placing a cheap space blanket between the bag and pad. It's crunchy sounding, but very effective.
My wife and I are in our mid 50's (I say this because you are probably more suitable to the cold then we are). We took the bag down to 9 degrees and were perfectly comfortable and warm. Pad stayed under us at all times. My wife and I had no problems carrying the weight involved. For a zero degree bag it is indeed heavy, but the quality of the bag is supreme and worth it to us.