Sneasle,

Add some triangular stock along the base of the rudder where it attaches - adds a tremendous amount of strength. I use that on a lot kits also while I'm building them up. I'll try to send you some pics later tonight.

Hogflyer

Edit: found a picture of using a piece of triangular stock to brace up a tail. This particular example is on a Balsa USA Stick 30, and the tail just butt joints to the top of the horizontal stab. The triangular stock is what provides the strength.