You can make things very easy on yourself by using a threaded control horn on the rudder. The DuBro kit is good quality and is what I used on my 50cc Extra. I used a 3 inch long servo arm for direct pull pull control with the cables not touching anything on the way out to the rudder. Yes, I wound up cutting a really long slot down the sides of my fuselage which guys at the field will comment that I could have avoided by crossing my cables, but you can't see them in flight! With the threaded horn, you can do a fine adjustment of the length to compensate for any geometric issues that you have. If you see that the cables get tighter when you deflect the surface to the left and looser when you deflect the surface to the right, you shorten the right horn and lengthen the left one and try it again.