Classic reply..
4 degree seems to be the best all round solution for just about every track..
You have to wonder what setup would require a change in this area to get the car working better, never heard anyway say "Changed to 6 degrees .2 right there!!"
Never had a setup which changed from 4 degree personally but each to there own...
TF6 just works put on one of Mr C.Krapp or Mr C.Vasco setups and your car will instantly be a great car to drive