Just a suggestion.
Look around for a reliable, well respected audio installer. Someone who does cars, boats, RVs.
Either they can do it as they understand the same idea that's used on cars and boats running auxiliary batteries with their sound and video systems.
We have a local specialist that does cars, boats, RVs, planes, and UTVs from locals to ask over the United States and Canada.
A Fed Ex executive flew two brand new SxS from Alaska to Dallas and trucked them here. They did over $100,000 in upgrades, including a $35,000 sound system with custom boxes built with a system that is a 3D or 4D CNC saw system. I've seen the results, but not watched it run. Then they were crated back up and returned them to Alaska.
It's just a matter of asking around and you'll find a knowledgeable, competent person who will do you a job that's not a rat's nest, but rather looks factory original or very custom.
Good luck on your project
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