if you have a throw gage that is the way to go,i use a tailors tape and set it up on the rudder about at the 5 inch mark to the center of the elevator then measure from looking at the tip of each elevator to the tape.get the linkages right first and the control surfaces as close to neutral as possible then measure from there then you can set your radio up if it is a computer type for the throw rates.after i trim out an airplane i will use a angle gage i make out of Popsicle sticks to get the servos back to center the angle gage is used to get a measurement on where the surfaces want to be centered at.some planes like a little up or down elevator to fly straight i guess because of warps or just the characteristics of the planes.most of my planes the surfaces are normally centered,i have a super stick that likes a little up elevator to fly straight.