moving batteries under console

[Cheg]

I just returned Nigel Calder's book on boat wiring to the library so I can't confirm the percentage, but copper conducts significantly more current than aluminum per. mm.(30% sticks in my mind ?) He recomends copper with adhesive lined heat shrink at the connectors. If its 15 feet to the motor use 30' (to and from) in the charts. After reading the chapters on batteries and wiring I've decided to place my main cranking battery much closer to the motor with another battery in the console and tieing them together, with a selector switch, with something around 2awg. If someone knows a reason why I shouldn't do it this way I would appreciate some feed back.