Buccaneer: Your advice is really helpful, thanks. I mentioned last that I was thinking about going for the 20° Incubator, but I've yet to actually pull the trigger on either of them. I'm waffling, big time. It would be the easiest decision to make if it wasn't such a subjective, personal thing. A 0° might be comfortable up to 65° for one person and 45° for another. I don't know if I'm a warm sleeper or a cold sleeper; all I know is I like tons of blanket in the winter and a thin sheet in the summer (indoors).
I'm leaning towards the 0°, but my decision is also affected by the fact that it's now warming up and any of the underquilts are big purchases to not be using for another 7-8 months. In the mean time, I'll just use you guys as my outlet until I make a final decision.
Thanks for the clarification on the overfill, Bubba.