After 30+ days in my Peapod last winter experimenting with different hammocks and additional insulation, my conclusion was that my Peapod was best for me just as it is (no extra insulation except for my fur hat). My temps were cold but never went below 20º. For the initial warm up laying in-line was was the best way to warm up. Even then I'd always wake up diagonal. If it ever over heated, a little knee action upward cooled me off quite nicely.
Bottom line . . . . . . I LOVE MY PEAPOD ! ! ! Now that it's summertime here I'm back in my BB with a te-wa UQ, and I love 'em both.
"Well, you might be lazy, but if we were not all about comfort here this would be a tent forum!" - - Roadtorque