I also use the "removable key turn thingy". It is mounted on a bracket on the dash support tubes. For security purposes remove the key and take it with you or hide it somewhere in the car. For safety purposes you want the turn off within arms reach or where others can get to it easily in an emergency. Like an electrical fire while driving down the road or a stuck throttle.
Just two of the times that I have been glad that I had a cut off switch.