TWO RANDOM POINTS
Parallel means running alongside. Do not parallel either line or neutral to a 12 volt positive or chassis negative wire closer than 4" and then for not longer than 10 cm. This stops a lot of noise from entering the 12 volt line which can affect sensitive electronics, radios, televisions, etc.
Instead of using BLACK as 12 volt chassis negative (ground), use YELLOW. This is being universally adopted in yachts. For a damned good reason. People have died from touching a black "Battery Ground Wire" thinking the live 120-volts was "ground". A battery only rig needn't bother.