Bob,
I highly recommend Nigel Calder’s book BOATOWNER’S MECHANICAL AND ELECTRICAL MANUAL to help guide you through making any electrical changes, modifications and/or upgrades. All the tables and data you need are in that book.
Keep in mind that the battery cables need to be sized to minimize the voltage drop in the run, preferably no more than 3% loss. The length of run is the total ROUND TRIP. Over current protection (fuses, circuit breakers, etc.) are there to protect the wires not the devices, so if your electric winch is tripping the 50A breaker, make sure the wire is large enough for the load before going to a bigger breaker.
I also moved the batteries forward in my previous WC30. My new boat has a very minimal electrical system, but Im already making big changes.
Tom P.
Wyliecat 30 - DAZZLER