Battery relocated in trunk.

I am likewise planning a Ford relay in the trunk to keep the positive cable dead except during crank. And I'll have a 4ga wire (fused in front and rear) running from the alternator to the + side of the battery in the trunk and a 2nd separate 4ga wire fed AFTER the master disconnect (and fused) will bring power to the front of the car to provide power for everything. The battery cable will go straight from the + terminal on the battery to the starter since it's cold except during crank. This schematic allows the master disconnect to kill the engine, fuel pump, etc (although I'll also have a fuel pump disable based on the engine not running). The engine is a 10.5:1 CR 408 so nothing exotic.

So my question to the forum is what size battery cable do people use...I'm thinking a 1/0 size should be adequate but interested to hear from the experience of those that have "been there, done that." Thx!!