Lets say I need 2" of elevator throw,..... I could use a 2" servo arm with a 1" control horn and achieve my desired 2" of travel.... or .....I could use a 1" servo arm and 1/2" control horn and get the same 2" of travel.
Which way would you do it and why?
I would always use I could use a 2" servo arm with a 1" control horn WHY the load in the control rod is half and the slop at the control surface is half.
Use the shorter arms and horns you will get more slop and a greater chance of the control rod deforming.
bur here is the clincher YOU ARE MUCH MORE LIKELY TO GET FLUTTER WHICH IS AN AIRFRAME KILLER.
Longer [and stiffer] is better.