I've just placed the general kill switch (aka contactor or maintenance switch) in the transmission tunnel, next to the hand brake:
The holes were not hard to do but I did have to buy a 68mm hole saw.
Here's the view from the underside:
There's enough clearance, even considering the transfer case might move a bit. There's also clear space to wire the thick EV cables and conduit front and back. I will apply some sort of sealant (and paint the cut metal of course).