I just made a drawing on AutoCAD and What I got is really interesting.

With 60 degrees on the servo each side and a 3" servo arm (1 1/2" each side) and a 3 1/2" control horn on the rudder 48" from the servo (hinge line to servo output spline). The results are 0.009" slack in the cables ----> negligible. This was done with cables "parallel", not crossed. I get about 45 degrees at the rudder.

Now I can use a single 5955 on the rudder of my big plane.