I remember seeing that box on your older website. One of the best thought out I have seen.
As Jeff posted batteries should be near the engine. Size wire for any load for the desired voltage drop. Even with a large load like a windlass or thruster forward a battery in the bow seldom makes sense. If you are using an ACR between the aft and forward banks the wires run will have to be large anyway. And then there is the maintenance issue of another battery in some cases - less of an issue with AGM batteries.
Living aboard in Victoria Harbour