Thanks again for all the help. My solution was:
- Pull the roof plug
- Use the existing roof hole, and drill a hole through the roof of the wardrobe cabinet directly underneath
- Run 10 gauge wires through there down to the battery.
Not as pretty as running the wires inside the walls as the factory ones would be, but it's basically a direct shot down to the battery compartment and the wires are only exposed outside of the cabinet for about 2 feet total, so not bad. I mounted my controller inside the wardrobe.
Just came back from a week trip including a few days in Death Valley and the solar worked great, and it was super nice to have. Thanks everyone for the help! And now I have the capacity to easily add another panel, the 10 gauge wires are certainly nice to have.