Here are some images of my setup. Running a battery box from on top of the wheel well. I figured i can't use that area for storage (things roll straight off it) so i mounted a bracket to sit a battery on. It is bolted into the car frame at the wheel well and the battery is strapped down with a ratchet strap. Under the bracket there is also a storage hole where i keep ratchet straps and battery cords etc... I have had it in for about 6 months now and used it highway driving and off roading and it doesn't move or come loose at all. Works very well when camping, just have to have the door open to run cords into it, or if need be, the door can still be shut. Also the box tucks away nicely so that the back seats can fit in and out of the car still and it is out of the passengers way.
You will also notice the false floor that i made and installed. I did that so i can mount a fridge into the car and not have to drill into the car itself to mount it down. The floor also works very well and i bolt it into the back passenger seat mounts and as a secondary mount i use the small clips next to the door.
The cargo barrier is another great addition and allows me to stack things up all the way to the roof without fear of it flying forwards into the driving area. With the fridge and battery in there is still PLENTY of space to pack food and clothes, tents, recovery gear etc... I have had this setup for quite some time now and used it for road trips out west and offroading and camping and i am EXTREMELY pleased with it functionality and performance