Didn't notice if it was mentioned earlier in the thread so I'll just mention, regarding electrical safety. The major concern with 12volt DC systems is burns from shorting wiring or tools. Accidentally getting a wrench across the terminals of a battery makes one hell of a spark and melts the end of the wrench... So I've been told.
Disconnect the batteries when working on the wiring unless voltage measurements are being taken, etc. I like to wrap tools with electrical tape if I need to work on live circuits.
Best of luck.