Since I'd originally started this thread, with a very narrow, specific question, I just thought all the folks who had shared a lot of really good information with me might like to know how things worked out.

Actually, the clothing was planned, not just luck. I'd assembled the whole system after reading the same posts you did that said you should wear everything. Like you, I don't agree with that; I'd prefer to use clothes as a safety margin. So, I assembled my gear with the idea that I wouldn't really head out if predictions were for lower than 20 degrees, and that the clothing would provide a 10 degree safety margin if one night got a bit colder than predicted. The trip I described above was simply one of those rare opportunities you get to test out your theory in a "safe" environment, where I could have walked back to the car pretty easily if the theory fell apart.