I don't have my colregs in front of me at the moment, but I seem to recall reading somewhere in there that multiple lights within a certain distance of each other (half a meter?) can be considered one light for the purpose of the regs. Two 180-degree lights on opposite sides of the mast would thus be considered a single 360-degree light. IIRC, YMMV, IANAL, etc.
1979 Gulfstar 37 Laissez Faire