If the coach is pre-wired, it's likely too small a gauge wire anyway. Usually easiest is to run under the refrigerator vent, down behind the frig (open the outside access panel), then you can go where ever you need to go.
The controller is best located nearest the batteries if possible. A goal is to keep the wiring as short as possible.
Here is an example using a combiner box to go under the frig vent.
Refrigerator Vent C-Box | Combiner Boxes