not necessarily, the 'double' suggestion is comparing 12V to 6V because 6V draws about double the current, forget the "doubling" and just deal with 6V item specifications - the fuse should be a size above the rated draw, usually you just use an available standard size above the items rating, 4,5,6 amp fuses aren't common sizes, 7.5 is, and you have 2 back up lights, not just one? ... you want to avoid using a fuse way above the item rating, like not a 30a fuse for the lights, try to find the amp draw of anything you use and fuse it slightly above that
Bill
