Setting your ATV to maximum will give you more servo rotation, maybe +/- 60˚ instead of 45˚, but no change in mechanical advantage.
Setting the ATV at maximum gives more mechanical advantage
indirectly by allowing you to use a hole closer to the center of the servo arm to get the same surface travel. Maximizing the mechanical advantage of the control linkage requires that the servo travel be set to maximum before you select the position of the pushrod in the servo arm to get the surface travel you want.
Jim