It takes me about 50 flights to get an airplane really flying well. I will get it about 85% there on the bench before the maiden. When I start making changes I fly with that change for a bit before making a decision if it was a good or bad change. For your setup, I would start with 2.5 to 3 degrees. If that gets you close you can fine tune with a throttle/rudder mix. The only issue with that is one would have to have good throttle management. If you have a habit of being at either idle or full throttle when you fly then the mix won't wotk as well.