To clarify, I'm not opposed to one on the underside of my car, but I have it wired up currently inside with a hidden compartment near the spare. The wiring currently allows me to switch between 4wire and 7wire, already linked, one running into the other.
The move to mount exterior would mean more fiddling, and likely a bit of a headache, as the trailer has it's own trick to work with: the tow wire is secured static about 2 feet behind the hitch on the frame. (i didn't do that, but I also don't really have any interest in having to add a whole new set up of wires and also link them to the old trailer wire.
Our winters are of course just winters. Here there is considerable salt used on roads.
I was talking with the local trailer company and one thing they did say was they see a good deal of corroded electrical
tow related issues.
Given what I have to work with, making a short extension seemed the simplest.