Mount the servo and the rudder control horn. Mark the servo arm height on the side of the fuse. Stretch the cable between that mark and the rudder control horn, mark where the cable touches the fuse near the tail. Do the same thing from the bottom. Mark where the servo arm is on the bottom, stretch the cable between the two points and mark where it intersects with the line marked on the side of the plane. Pop a hole in the side and fish a cable in there to check how it lines up. Then make the hole into a bigger slot when you know where exactly where the cable will move around. Normally the control horn goes towards the bottom of the rudder just because that's a convenient place. I attached a pic of one I made outside the fuse. You could do that also on the bottom of the plane. A also attached some of my CAP232 120. I crossed the CAP232 cables. One cable is slightly slack when at full deflections but it does not cause any problems after many flights. Also my cable goes through some antenna tubing that I CA'd to the side of the fuse. This keeps the cable from rubbing on the wood. Some people will say to not have it touch anything as it goes through the fuse but it doesn't cause any problems at all.