I assume I am in "Trim" or "Balance" when something centers....be it string, ball, or pedals....in no particular priority. The best indication is when the wind quits roaring through the cockpit doors in one direction or the other.
Do you guys lay awake at night thinking about answers to such questions?
If so...ponder this one.....
If you maintain the aircraft in "trimmed" flight....how much offset do you add to the formula determining the correct heading to be flown to fly a particular track across the ground from your Takeoff Point to your Destination?
It would seem if this TR drift thing is so significant...then CFS trained Instructors would have a colored pencil designated to depict that bit of the Vector Diagram.