I Bought an Mx3 Air as well but went with the Hi Tec 625MG servos Z plug for airtronics. They seem to have the torque to do the job and the speed as well for the $.They Run in the $40 range each and the metal gears (MG) Help through the early break in periods of getting it right.The basic things in setting up your servos to work right are to make sure that when on your Steering You Go Full Right or left that your servo doesn't stop before you are all the way turned and that both Right and left are adj. equally. You need to retard your steering accordingly by means of your Steering endpoint adj. on your Radio transmitter for that.Same with the Throttle But you probably already Know this.Budgetwise Any Bottomend Nylon drive ,speed for $ Hitec 625MG ,Hi end coreless and digital Money To Burn 1:1 Forget the servos.....
