With all of that equipment to hook up, having a ground buss back there makes sense to me. You will need a larger wire to go from the buss back to the battery. Remember it is carrying the current of all of the items that are on at the same time. So if everything together has a 10 amp load, then I would size my wire accordingly. It would be rare that you would have it all on at the same time, but if you did, the wire would be large enough.
I used a wire sizing chart when I did Miss Morgan, A good one will show you the size of wire for a certain length. The longer the run, the larger the wire. 12 volt systems are suffer voltage drop over long runs, thus the larger wire. When in doubt, use a bigger wire!
Most of your equipment should have some sort of power rating on it, say a 40watt light. The problem is that you know the voltage is 12V, but what is the amperage? Easy, 40watts / 12 volts = 3.4 amps. Once you know the amps and the approximate run length, just look up the wire size on the chart. This will also give you a good idea what size fuses to use on each circuit.
I did a drawing, which help a lot! I also color coded some of it black for all grounds, red for main power runs from the battery, white for power to lights, blue for wires going to sending units, etc.
opcorn: Looking forward to the updates!
