I will partially disagree with kdheath. I have built a couple of airplanes with adjustable rudders and, just for kicks, tried them in different configurations. If you crank the rudder out you can increase line tension in level flight to a great extent. Notice I said level flight. Take the airplane up high and it is likely to fall in on you because of excessive yaw.

A Rabe rudder, invented by Al Rabe, is a rudder coupled to the elevator such that the rudder moves in a specified manner when the elevator moves up or down. There is a complete explanation of how and why on Stuka Stunt Works Control Line Forum.

Jim