Yes . . usually from the prop shaft where it exits the nose. This should be pretty close to center. Tape the rudder in the exact neutral position, and have a helper lift it by pinching the trailing edge of the rudder on or just above the longitudinal? CG. Then add weight to the light wing tip until it balances.

I have found this method to be very close, with possibly only minor adjustment after the "inside/outside loop" test.

Cheers, JB

PS. The rudder trim I test by flying away from you directly into the wind (no wind is always better) in a 45 degree upline. Trim the rudder until it flies up straight, then roll to inverted half way up and see what it does. If it veers to the left or right, adjust the rudder trim again until it flies straight while inverted in the 45deg upline, then recheck the upright. If you end up with a compromise where it will veer slightly one way upright and the other way inverted (which is actually still the same way), the model is llikely to need a thrust line adjustment.