Consider this.............

It's very worthwhile to control your model's takeoff direction with the rudder. A vast majority of modelers will agree with this. Even the "you oughta learn to fly the pig and you'll be a better man for it" crowd.

So what do you think happens when you've got your model blasting down the runway, it's a tail dragger and the tail has come up, and a bump turns it towards the pits, and you hit the rudder stick to turn it away from the mother with twins in the stroller who has just brought hubby a sandwich for lunch and walked right past the sign that says "Only flyers in the Pits" ???????????? Hooo Hahahaaaaaaa, it's time to turn, right? or left? And what happens?

The rudder tries to pitch the nose down with that rudder movement. And it's doing the pitching as fast as the yawing. And the gear is keeping the nose from pitching down, so the airplane does what it can do and the tail goes up some. And then the nose does sorta pitch down. The gear spreads out, the prop starts eating dirt, and the mother has to throw her body in front of the stroller and.......... Man, some days at the field just go SO wrong.......

whatever..............

It's usually worthwhile to have a rudder that only makes the plane yaw.