Remember the newer rudders are shaped differently as well. What I would probably do is find the center point on the bottom of each rudder, measure from the bottom of the transom up the bottom of the hull 40 inches, mark it. With the rudders in the locked down position measure the distance from the center point of each rudder to the 40 inch mark on the hulls and try and get the measurements as close to the same as possible. I have been using this method for a very long time.