I did try out the use of the vapor barrier principle on this trip in 2006. After shopping around for vapor barrier socks, I decided to try heavy mill plastic gallon bags since it was an experiment. They worked tremendously well, my plastic boot liners and heavy wool socks stayed dry and my feet stayed warm. However, at night I when I was crawling into the sleeping bag I the light weight poly socks would be plumb wet with sweat. I'd put them between the 3/4 length thermarest and the ensolite pad to stay unfrozen. In the morning putting on the still wet liner socks at -10 to zero seemed counter intuitive to common sense. However after the plastic bag and wool sock were on my feet were toasty again. Since then I have scored some BD vapor barrier socks a the Jackson Hole thrift store.
I also have a full sleeping bag vapor barrier that I picked up at the thrift store. However, I just have not have the nerve to give the full body treatment the go.
When I was a pup I also traversed the Middle Fork of the Flathead and the South Fork of the Flathead in Montana. Also a number of shorter duration tours in the Middle and South Forks as well as the Tabacco Roots. Some folks just don't seem to be bright enough to come in out of the cold. And nope, the mosquitoes were not a problem. :-laf However, we did encounter several Bison bulls wintering along the Yellowstone. Basically, they would hole up, graze the decadent grass, and mostly live off accumulated fat.