I have a Smart Fly ignition cut off. This allows me to kill the engine by turning off the ignition power with a switch from the transmitter. I think an ignition cut off is a must for big airplanes because of safety, If the receiver lost its power (battery or switch failure) this immediately kills the engine. Nothing worst than a big airplane at full throttle without any control. I also use always PCM that brings the engine to idle in case of any interference.
For me with the size of these planes safety always comes first.
Andres