Slept outside Saturday night in the hammock, testing how the SS does with the reflective windshield cover from WM. Initially VERY warm in my 15 deg bag, and from previous testing I knew to ventilate. It felt like an electric mattress pad under me when I went to bed/hammock with temps around 60 deg.
Some nice aspects of the reflector pad as opposed to a space blanket was that it stayed in place very well, was very quiet, is much tougher than a space blanket, and offers a bit of insulation, which both helps with warmth and also, I think, with condensation. I bought the large size at WM--it's a space blanket laminated to a closed-cell foam sheet, and it folds up very nicely and compactly.
Toward morning I started to feel a bit cool on my legs (found out later there was a gap there), but my upper body was fine. Still could sleep well, but disappointed in the performance until I checked the thermometer--34 degrees, and not any condensation that I could feel on the windshield cover (I placed it between the hammock and the underpad).
Very nice--especially considering I was only wearing a synthetic base layer and wool socks. I could have worn some fleece and I think with adjusting the pad a bit I could have gone below freezing!