How to install a safe in the back wall of the closet? '07 Newmar KSDP 3912

[DGBPokes]

I see in top end Newmar's a safe in the wall of the closet. My KSDP has the same pockets for shoes that I see in the those rigs next to the safe. Hence, I am thinking that there likely is room since the end caps look the same. I visualize no problem cutting the hole, I can't figure out how to anchor the safe. I assume Newmar installed it during assembly at the factory. I have read here about other options, but I thought I would tap this pool of experts as to how to install it like the factory

["007"]

I would after the cut reinforce the plywood wall with 2x4's so you can attach the safe from inside the box.
You can nail and Liquid Nail 2x4's to back side of wall.
There maybe some wiring in wall cavity for outside lighting so be careful with cut.
There may also be aluminum studs in wall also.
A picture here shows back wall with 2x4's left of wall.
There will be insulation too.