Not sure what you mean by "unused O2 sensor ports" except that I'm assuming the "used O2 sensor ports" are the 12 mm ports for the OEM O2 sensors.
Just to cover all possibilities, there are two size bungs supplied with the late model VRSC V&H exhaust systems:
the OEM O2 sensors fit in the 12 mm diameter x 1.25 mm pitch bungs
the other set are 18 mm diameter x 1.5 mm pitch and are used by standard O2 sensors including the wide band Bosch LSU 4.2 that most dynos use