To my knowledge, you can only have one of each of the CMC units attached, with the exception of the FD of which there may be a total of four.
I don’t know for sure if this is written in stone; it was also stated somewhere that you could have a total of eight CMC units, but with four FDs plus all others this toal comes to nine - and I can attest that nine units do work together.
So if you’re in a position to test with multiple PDs, let us know. 