I've heard the claim that mounting the transponder on the chassis causes problems? But it has not happened to me. Another location to mount it, is double-sided tape to the Servo. Towards the front of the car, but behind the plastic guard the body velcro to. Be careful the wire does not touch the drive shaft. Either run the wire under the chassis stiffener, or use a little tie strap at the bottom of the chassis stiffener, when you go around the front.