I remove the springs on my gasser throttles and keep the throttle servo at least 10" away from the magneto or sparkplug.  That spring isn't going to defeat a servo that has lost power, and the failsafe should be set to lower the throttle to idle or lower if signal is lost.  If too close to the ignition circuits the windings on the servo motor coil will transfer the spark impulse to the receiver through induction (aka "EMI").  Less a factor with 2.4GHz, but still a factor.

At least that's the way I was coached on gas ignitions and servos.  Has worked for me so far.