Update:
I opened the two panels under the rear seat, and sure enough, there's more salt in there than under the fenders...
Too wet to do much about it right now, but when it gets more Spring-like, I'll pull the harnesses off, clean the terminals, and see what I can do to insulate the connections...
I'm kind of leaning to the liquid rubber that they sell to coat pliars handles with...It pours on thick, handens to a flexible rubberery coating...Cuts off easily; can be built up in layers; cures pretty quickly...