Went over the coach yesterday and found the answer. Under the bathroom sink, there is access to the duct/wire chase through a removable panel. It looks like all that is needed is to punch a hole through the coach floor under the bathroom sink and run wiring up to the switch panel wall. The bathroom sink sits above the rear axle but there is clearance to work.
The wire run from the chase up the wall is a good example of Thor's approach to craftsmanship. Why not just cut a huge hole in the wall of whatever shape it ends up. Looks like they devoted an entire 15 seconds with a Sawzall. At least it will be easy to fish the new wires.
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