I mounted my battery cut off switch on a metal plate that is on the support tubes that run from the under the dash to the floor boards. It is easy to reach while belted in and accessible from outside of the car for track use. Even if you don't ever intend to track your car, having the switch handy is important. If you ever have a your wiring short out and start to smoke you will be glad to have the battery cut off where you can reach it quickly. For security when the car is parked I just remove the red key that is the cut off switch and take it with me.
Dick