Gary, yes that was a bit vague. If the rudder control horn has the pivots 1/8" behind the hinge line then the pivots on the servo arm would need to be 1/8" behind the center of the servo output shaft. The offset has to match at each end in dimension and direction. Unless the servo arm is shorter and/or the cables are crossed then it starts to become a trial and error sort of thing unless you are a math wiz ( I am not so I keep things a symmetrical as possible ).