there's nothing in the 'walls', as factories don't typically use the walls for anything... and your wire from the panel down to the charge controller, and the battery bank, doesn't have to go thru any walls. Most of us use the rear of the coach, down the ladder, and up and into the chassis and battery bay, or a similar approach.
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
110,000+mi since '14 - US, Alaska, Canada (also, '14 Gulfstream Amerilite and '07 ForestRiver Rockwood) : )b