Allan,
I used the wrong word when I said "control horn". I should have said "steering arm"-the one with a set screw that goes on the rudder shaft. A pull-pull system would be both lighter and stronger than a solid rod from the servo to the steering arm. The attached picture is from a model airplane, but the idea is the same. The wires would go from the servo arms to each end of the steering arm (if it had two arms).