I added an 1 1/2" all along the back of the rudder and an additional 1 1/2" at the top so it forms a counterbalance tab all the way to the leading edge of the vertical fin. The plane will now hover and fly unlimited knife edge with a Saito .72 and a 13 x 6 prop.

A counterbalanced surface serves two purposes; one to give aerodynamic 'help' to turning the surface, and perhaps more important is to help prevent destructive surface flutter by changing the critical flutter speed just like a mechanical counterbalance does.

While you're at it move the CG back a half inch or so behind the factory recomended point and the bird will still fly well, but help in hovering and 3D response. Some folks go even further aft with more flying skill.

quint