On my IVP, I mounted a Piper external power socket and switch on the copilot side just below the battery box.  I placed a door in the upper cowl.  It is the same size and latch as the oil door.  I also access the pan heater plug from the same door.

I used the external power socket once with a jump when I left the master switch on.

Carl Cadwell

IVP 700 hours