Jay, you need more rudder servo. The servo you are using is not strong or fast enough to get the job done. I have been using a lot of Futaba 3305s. These are metal gear 99oz servos. Tower has them for $35. There are better servos out there but these are hard to beat for the money. You could also go to a 6V battery pack. This will make your servos faster and stronger on all surfaces. While the servos you have will fly the plane. They are not really up to the task of 3D flying
If one of these guys you fly with is pretty good. Ask him to fly and hover your plane. While practice will make you better. It would be nice to know if the plane is set up right.

david