I have been using a program to help me do just what these guys are saying

The program helps calculate the linkage angles as well as the torque required at any given airspeed.

I have just been doing an elevator that requires 1.125" up/1" down travel...pretty typical. But I wanted the maximum servo travel. Turns out an 8611 can be driven about 58 to 60 degrees give or take in each direction. I feed that into my program and I can play with the arm lengths to get it right. Now the servo travels to its extreme limits to get the required surface throw

I also got rid of clevises, I rarely use them now except for pull-pull installs that do not have linkage slop in the traditional sense. I use helicopter ball links and dubro large ball links on almost everything else.

Kenny did you get a second turbine for your F-18 yet?