I have this idea that I would like to try out for the upper body insulation in really cold weather but I don't have all of the stuff yet to try it.
I will explain what the idea is. I have read other's and I myself have a problem with getting chilled after about 15 - 20 minutes on the bike from the sweat that is suppose to be wicking away. Admittedly, because of the good wicking that I am getting the moisture builds up at the shell boundry and then acts to cool everything. It is something that I can live with but it is somewhat uncomfortable.
Here's my idea: Forget with trying to wick the perspiration and contain the warm moist air at the skin level using a wetsuit top as the first layer. No wicking layers are used but a neoprene wet suit top directly next to the skin. THen whatever insulation layer seems right for the conditions and then the shell or jacket.
Here is an example of an O'neil wet suit top for a reasonable amount of money.
I have used this approach with feet and it works very well and I would like to hear if anyone out there would be willing to try this and what thier experience is.