The reason for the prescribed process, is that the rudder cables have an overall length dimension tolerance and they vary in length slightly.
Properly sizing the links is how that variation is compensated for.
If the overall length ends up too long, portions of the pedal assemblies can contact the firewall before the rudder hits the rudder stops.
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Van's Aircraft Engineering Prototype Shop
RV-6A (aka "Junkyard Special ")