[Howard Jones]

If you only install one then place it inside the cockpit in a location that you can easily reach when you are all belted up. Assume you are hurt and can't unbelt yourself but can manage to flip the battery switch to save yourself from getting burnt up. Get the picture.

If you install two then place one as above and the other on the top surface of the body along the flat area in front of the windscreen. Imagine that the car is up against the wall and the battery switch is blocked on the side of the car. Or the car has backed into the wall and you can't get to it at the rear. You want it in the best location for a corner worker to get to it AND it won't get blocked by anything. In or about the NASA vent in front of the windshield would be my choice.

Lastly you can use a remote pull system with the lanyard placed as above.