It seems everybody's jetting is different when it comes to really cold weather. I jetted according to what lots of people recomended in the forums and after lots of trial and error and lots of spark plug readings. It turned out I was jetted way too rich everywhere and the bike just wouldn't open up. My final jetting ended up being 1 size richer on the pilot, one size richer on the main, and one clip position richer on the stock needle. I had similar mods with 10 - 20 deg. temps
Good Luck