is that -6 to -30 celsius or Fahrenheit?
The changes that I would make would be one richer on the main and the pilot as a starting point. Tis has to do with the air being denser in the cold which makes you bike run leaner. Adjust from there as necessary. Also, run lighter weight tranny oil as it tends to get thicker in the cold. I would not change you premix at all. If you do though, you may want to add a little more oil to your gas. This will help protect your top end a little better in the cold as things tend to get brittle. Also, due to the added stiction that the cold air provides, may want to lighten up on your suspension compression and rebound. May also ant to add more coolant to your coolant\water mixture. One last thought; Always make sure that you warm up your enine slowly in the cold. Never start it and then Immediatly crack the throttle wide open. Let it gradually get warm and then twist away. Have fun.