Hi all. One is reluctant to ask a simple question on these forums because of the temptation it is for some folks to be jerks. For the record, it's not apples and oranges, it's varieties of apples. Also, I'm aware I do not have a metal house, although I can say that on a farm outbuilding I once used a copper water pipe as a return with no problems. And I had a notion that most of my house is not DC, although there are some parts which are.
Thanks to SteveG for the first adequate answer. smkettner is also very helpful and exactly right. It's too late to change brands of box, though I like RoyBs idea of boat wire and will find some at a marine supply. I would rather bring the return back, though will use the chassis if I have to. After all, the box returns wind up back at the chassis.