I was thinking of a heavy duty blanket, like Cabela's http://tinyurl.com/2ggaay The lightweight foil type would be too flimsy. Letting it hang just a little loose from the underside of the hammock might take care of any condensation. I would imagine this blanket would be lighter than an underquilt, too. Sewing velcro to the underside of the hammock would facilitate removal of the space blanket for warmer weather. Since I'm hammock-less right now I can't try this.