Dang Wash hunter you got some tough feet...I got some 600 gram Irish Setters and do the same layering as you and I'm good to about 30. Then I bust out my 1000 gram boots.

Follow Dans plan if you want to stay warm...The key is to staying dry so when you settle in you don't freeze to death. Good luck out there and if you plan on making a roadtrip in Dec, expect cold temps.