You don't have to route the cable all the way to the bottom. I routed the cable out of the fridge cabinet through the interior sidewall near ceiling. This is a shared wall of fridge cabinet and top kitchen cabinet, easy 1/4" plywood. The exit hole from fridge cab was sealed with spray foam. So the cable length inside the fridge cabinet is only 1 foot.
From there it goes along the top cabinet near ceiling, exits the cabinet and continues along the ceiling all the way to the front of the trailer where it enters the bedroom cabinet - again near ceiling. Then down the sloped front wall inside the cabinet, and outside/down to the battery through the night table near bed.
Resistance loss depends on the current. Mine are 24V panels, 8A current at best, so I wasn't worried about this either.
