This is my rule of thumb,,
I use computer radio's and I set up like this...
atv/epa on my radio will allow servo travel to 140%,for the most torque and least stress and load to the servo you would start at 140% and install push rod as close to servo center and as far out on control horn as possible(I set at 135% to leave 5% to play with),at this point if your high rate control surface travel is short of what you want then adjust the linkage at one end or the other just enough to obtain the high rate travel you want.
this is the best for torque out of a servo and least load on a servo,,,however this also creates the slowest servo transit time so if you need more speed you would head towards the opposite end of this set up or better yet find a servo with the same torque rating but a faster transit time.

For what it's worth!