My 2 cents.
Two points of interest here:
1. Control surface throw and
2. Slop
Number one, the length of the servo arm and control arm only effect the control surface throw when the ratio changes. To visualize this, think about a belt running around two pulleys. As long as the two pulleys are the same diameter, they will both turn at the same rate. ie. Move one pulley 45 degrees, and the other will move 45 degree as well. But if you make one larger than the other, they will no longer turn at the same rate. A side note regarding torque, provided that you don't change the servo/control horn ratio it doesn't matter what length they are, the same amount of force will be applied to the control surface. In the previous example of 100 oz/in @ 1 inch causing 133 oz/in @ .75 inch is correct, therefore the force applied to the control rod is increased. But at the other end of the control rod that higher force now has less advantage on the control surface due to the shorter horn.
Now as for number two, the entire control setup is about motion translation. Rotary to linear and back to rotary. Any slop involved in the rotary component is related to its turning axis, and doesn't change regardless of radius of movement. ie a berring is going to have the sazme amount of play when installed in a two inch wheel as when it is installed in a 2 foot wheel. But the linear components slop is relational to its size. The linear slop comes from the size difference between the hole in the servo arm or control horn, and the pin in the clevis used. This slop can be measured, it is small though but consistent with all lengths of servo and control horns. Now we need to consider the amount of distance the control rod will travel. The longer the servo and control horns are, the further the rod wil move, and vise versa. Therefore, the more travel you can get in the control rod, the less effect the slop will have.
Sorry for going so long and confusing, but this proves to be a hard topic to explain without pictures and hand gestures.
Note: I would put in a lol, no wait LOL but it appears to be a fopaw to laugh at ones self here. ( please see lol ettiquete thread )
Steve