And, it comes down to resolution (precision) of the control. Generally, the longer arm hole will give you less resolution. There is a whole discussion about that in another forum. I will try to find it and post the link.
Meanwhile, as far as the throttle setup is concerned, well, the discussion was about the Futaba Skysport, which does not have end-point adjustments (as in your typical computer transmitter). Here is what I posted in the other thread:
Because the Skysport does not have end points (not a computer radio I believe) you have to do all this mechanically. The stick movement relates to 100% servo movement. So, you have to work with the mechanical settings of the "levers and bell-crank" action of the servo arm and the thrlttle arm.
First, zero the servo . You can only do this using one of the other channels with trim set to the mid point or at zero (no plus or no minus trim, just set it to the mid point on the TX). Connect the servo to that channel (rudder, elevator, aileron... whatever, but not the throttle ). This will set the mid point of the servo . If the servo arm is not 90 degrees to the side of the servo , then remove the servo arm and rotate it 90 degrees. Each arm is offset somewhat to enable you to find the ONE of the four arms that are the correctly centerd ones for that servo . If you do not have a four arm servo , get one.
Next, center the throttle on the TX and again, center the trim. Then, once you have the servo centered and the correct servo arm selected, then you can cut the other arms off... or not, your choice. Install the servo , or if installed, plug it into the throttle port on the RX. If it does not "rotate" correctly, then use the throttle reverse switch on the TX and get it right. The throttle arm on the servo should now be centered. Do not touch anything on the TX. Set it aside, yeah, leave it on.
Open the throttle on the engine to what you think is mid throttle setting. Set the trim to fully closed (all the way in) Now, use the hole on the servo that is the furthest away from the center and the same on the engine throttle arm. Adjust your linkage so that they match up. Lengthen or shorten as necessary. Connect the throttle linkage. Now, slowly move the throttle until you go to full open. IF no bind, then go to full closed. If no bind, then you are ok. If it binds, then re-center it, chooose a next hole on the serov that is closer to the center. Leave the one alone on the engine. Re-check for binds and that the throttle opens and closes fully with no binds. If no binds then you are ok. If it binds, then more adjustment is necessary. Continue to adjust as necessary until you are happy that it opens fully and closes fully wiht no binds. NOw, you should have correct adjustment and trim settings so that you can close the throttle with the trim to shutdown the engine when finished.