You will hear different opinions on this matter. Some say 8" and others will say 12". At 11.5" you are fine. Just make sure you do a ground check with your radio with the engine running. Perform your check at idle and at full throttle.

I think that most people are clamping the ground wire right to the base of the spark plug with a hose clamp.

As stated in an earlier post. An electronic kill switch is a good alternative to a choke servo.