If 0/2 is overkill then thats most likely what I will go with.
I appreciate the input.
That first link brings up another question for me though. when wiring the batteries, I understand the benefit of positive off one end and negative off the other. But when series/paralleling 6 volt batteries does it matter what "series" of batteries the cables see first? For example (this is visualized in the attached diagram, sorry for the roughness) my current setup has four batteries in a row, two are together in a series and so are the other two. The paralleling cables will both hit the two batteries to the right first. Does this break the "rules"? If so, would having extra negative cable as in (A) be best. Or just have the cable come out on the other side as in (B)?
It helps to know that the panel and all other components are to the left of the batteries. Which is where I would like my positive and negative Busses to end up.
A second question that comes up, regards the placement of an echo charger, AC Battery Charger, and any other electrical components. Is it a horrible idea to mount these in the engine compartment close to the batteries? Not so worried about diesel fumes as much as corrosives from the batteries venting, oil, grease, etc.
Thank you for any and all input, it helps get the mind going.