RickP,

So you have an actual fiber cable going to the engine area and use that to trigger a relay or a fet or something? It then has to have it's own battery.

Some of those aerobatic birds are getting huge so I would worry about long leads too.

On Cliff Sands Knight Twister, he had a 4.4ci with a magneto and we had an RC kill switch in the engine compartment. Never had an interference problem and the motor was very close to all the radio gear.