Gotta have a diagram to keep my head straight.
I'm not going to put the switch on the shifter. When I'm NOT hypermiling, I don't want to accidentally bump the kill switch. Plus, it wouldn't work with my solid steel knob.
On the Miata, I put the switch right next to the shifter. So, I'd pop it into neutral and bash the switch. It worked, but there was a bit of a lag because I was doing it all with my right hand. So, here, I think I'll put the switch in the stock start button location (there's a blanking plate there now) if it's close enough that I can hit it with a finger from the steering wheel. I'll have to go look at the car a little closer before I commit.
Another possible location would be below the AC controls, directly in front of the shifter.
Or... I guess I could mount the switch on the stick a little below the knob. (my shifter boot leaves a couple inches of the stick exposed due to the knob I'm using) That could work. And if I do a bypass switch... that would allow me to disable the kill switch when I want to be sure I don't accidentally hit it.