Been thinking about the pro's and con's of this for a while and the various options.

when I put a second battery in my disco 2 I had it in the engine bay with a split charge relay and the second battery is for my winch so not available for starting but for the RR I need it more for starting.

The additional location is the boot and the cables to and from the rear fuse box (I Believe) are not rated high enough to allow a starting current especially with a low main battery.

So, what are the options (if any) for running extra high current cables from the rear into the engine bay putting both batteries in parallel and avoiding the rear fuse box all together?

or am I completely over thinking it and go with what's on wiki

I have a second battery in the boot area simply wired in parallel with the front battery using the existing 100A cable supplying the rear fuse board. I deliberately disconnected my front battery, left the car for a couple of days in cold weather then started it using the rear battery only simply to see if the 100A cable would be ok.
It was, as was the 100A fuse. I couldn’t guarantee the same result in freezing weather but you never know.

I fitted a second auxilary battery, Second battery in boot supports all systems when ignition off, main starting battery for starting/running isolated when ignition off, reconnects when ignition on via a 200amp relay, original heavy duty cable direct to starter still in place, only the system connection isolated, so ZERO drain on main starting battery, both charge with split charging wiring when running, and 13.9 lovely volts. Fitted a digital voltmeter in place of analogue clock, which I've kept, as android head unit has Internet time aligned display in any case.. Second battery connected with an 80amp resettable trip in-line to protect vehicle loom...

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