Dear Mark,
We can assume the PMP450m and PTP670 are working on the different channels but on the same pole. We understand this is difficult. With the cental site (Site B) having both PTP670 ODU set to Master, the other two sites will have one Master PTP670 ODU and one Slave PTP670 ODU and the PMP450m. Or, as you mentioned, we locate two Masters at A, and two Slaves at B; at C we now need one Master and one Slave. This is the reason why I want to have a solution.