David servos can be moved by hand when they are receiving no power so when you turn your system on they will often glitch slightly and move to the neutral point that the tx is sending them.

To set up a new servo installation: Remove the servo output arm from the spline shaft then install the servo--- Set your Tx's manual trims to neutral--- Set the Tx's sub trims to neutral or zero (I cannot be more specific on your radio because I stick with Hitec and Futaba)--- Power up the system--- The servo is now at neutral, install the servo output arm back on the spline shaft perpendicular to the to the pushrod (not necessarily aligned with the servo case.

Your servos will now return to the same place every time you power up and you can now continue with the pushrod fabrication portion of the installation.

The above procedure can also be done with a simple device called a servo driver that is plugged directly to the servo and it will positon the servo to neutral for you (plus a couple of other handy features) so there is no need to power up the entire radio system when installing sevos and fabricating pushrods.

John

Oh by the way, welcome to RCU