I've never quite understood the fascination of these master cutoff switches. We have 8 vehicles and not one of them has a cutoff switch installed from the manufacturer. On top of that, as noted above, it will not kill the engine since the alternator continues to provide power as long as the motor is spinning. My Cobra has an ignition switch with a key, why would I need another key? I put the key in, turn it two clicks, the engine starts and the key springs back to the run position. I don't even have one of those silly push button start switches. Just one humble builders opinion but if you're not racing it within a sanctioning body that requires it, why bother.