I built a Goldberg Tiger 2 last year, and of course I kit bashed it. I enlarged the rudder and elevator, and made it into a taildragger. Well, when I enlarged the rudder, I just made it bigger, with no regard for following plans and aerodynamics and all that crap. As it turns out, my larger rudder causes the plane to pitch (violently) to the belly at full rudder deflection. I did what you did, mixed it out with the radio. But inquiring minds had to know, so I have asked several self proclaimed experts about the problem. The consensus is that since my rudder is larger at the bottom than the original, it is stalling out the elevator at full deflection, thus mitigating the effeciveness of the elevator. In other words, the rudder below the elevator is now large enough that at full deflection, it causes a type of vortex (for lack of a better word) under the stab the acts like down elevator.

Wether this is true or not, I cannot say for sure. What I know is that the Tiger 2 is a great little flier, and THANK GOD FOR COMPUTER RADIOS!!!