Draco and I were talking to a motorcycle tire guy a little while ago and he said that running 42 front and rear was recommended for most conditions

But if you want best mileage run 50 to 55

This will lower the heat in the tire but will also lower the grip, on the plus side the tire life will greatly improve

Personally I run 42 front and 45 rear and find this is working out great so far

Cheers
Shiney