Actually the primary system battery is roughly 15v, that would be a lot of wasted heat to linearly lose in voltage drop! So instead I am going to power the lighting system with a switching regulator that can provide 4A at about 5.2v. Series would be preferred but the voltage isn't quite enough, I don't know if the UBEC's I have coming are switchable to 6v, if it is I will just run those two in series, there is a .5v drop on the current sink too to keep thought of, that puts the theoretical need at 6.5v, however the green LED is spec'd down to 3.4v, so 3.4v + 2.2v + 0.5v = 6.1, and if the UBEC has 6v selector realistic output will be 6.2, I actually have another 7A UBEC that puts out 6.2, I might just use that one.