You must use a polarity-reversing switch. It works the same as the power windows in your car. Put the switch in one position and one of the wires is positive polarity and the other is negative. Put the switch in the other position and the two wires change polarities. I'll go see if I can find a diagram.
Thanks, Guy. I have also seen the web info on the OGM reverse polarity switch for the two-wire method. What I don't know is if OGM manufactures their LED combo masthead lights in a particular manner which allows that to be done, or if all LEDs will work with that same switch mechanism. As I understand it, that switch does nothing more than switch the polarity of the two wires; i.e., when the switch is thrown, the two wires switch from positive to negative and vice versa. So I'm wondering if OGM has modified their diodes at the masthead light, or if the Lopolight masthead diodes will function exactly as the OGM ones function. Any thoughts?