Andy,
Ditch the stock rudder! It is way too heavy and the hinging is awkward. Building up a balsa one is far easier than you think...I put one together in about an hour and it came in at about half the weight....most of that mass is close to the hinge line. As has been discussed earlier, the stock (80+ gram) rudder has much of the mass aft of the hinge line...a bad situation and a receipe for flutter.

-Erik