I'm thinking about a new underquilt, and since I have the HG hammock with net, and the HG tarp, I'm leaning towards the HG UQ. Can anyone tell me of the temp ratings are truly more like a comfort rating or more like a survival rating? I am well aware that there are many variables to consider, but as a general trend, if I were camping in 25 degrees, would a 20 degree HG UQ keep me warm, or just keep me alive?