This is taken from post I made on another forum, Uncle Scotty also helped me a little via PM. This setup has been running in my car for a couple of months now.
This is most of the parts I used to wire it up
I'm using a 150Amp inline fuse, I mounted it right next to the battery but later found this was not the best place if I ever need to change the fuse with ease (hopefully I won't need to)
I used 6 stainless steel pop rivets to mount the tray to the floor pan
The 4 gauge power cable runs through the center console and out into the engine bay, it then connects to the back of the starter motor.
I used some protective conduit on areas with potential sharp edges.
Almost ready to connect up. The earth is on the seat bolt (sanded off the paint there) and there is still the factory earth from the engine block to the engine bay inner fender.
This explains the wiring
All installed now, this is with the seat pushed all the way forward, access to the battery is very easy.
Battery-less engine bay, 15kg off the nose of the car.