YOu don't need an adjustable servo arm with the 9C.

You need to adjust the max and minimum throws. This can be done in the transmitter. I have the 9C and it is a very versatile remote. Look for the End point (Endpt) adjustment in the menu. Once there, select the throttle channel and reduce the high end setting until you can open the throttle all the way and it does not bind, do the same on the low end.

The "throttle cut" feature is also very nice to have. It allows you to turn of the motor without using the trim button. Read the manual, it explains fairly well how to program that.