I posted a reply here earlier but my information was evidently not correct -- sorry.
It appears that the best way to re-center the rudder control is to make the adjustments in the rudder hatch (shown here):
I would suggest proceeding as follows"
1. Retract the rudder, automatically centering it. Open the rudder hatch with a Phillips head screwdriver.
2. Loosen the two Phillips head screws on the bell crank(?) that secure the rudder lines.
3. Center the rudder control in the middle of its arc of movement. This is about 30 to 45 degrees toward the outboard side of the seat, depending on which side it is mounted on.
4. Remove any slack from the rudder lines and re-secure them with the Phillips head screws.
5. Test the system to verify equal deflection of the rudder in both directions.
6. Replace the rudder hatch.
7. You can make final tension adjustments with the knob attached to the bottom of the rudder control pod.
