Take a piece of pull pull cable and pull it tight between the control horn and the side of the fuse where your rudder servo arm lines up. Mark a line on the fuse near the tail that follows the cable. Do the same thing but pull the cable tight above the fuse and eyeball where the cable will go through the fuse. Mark that location. That's about as close as you can get without laying the entire thing out in a 3D model in CAD.

Joe