Hi Mr. Plume,
in general, the PS8810 is no IQ Controller, that means, it is only possible to control functions inside a single PS8810 by the local control port.
There are two possible solutions which I know to solve your problem:
1) with a dummy signal
If the control port at the PS8810 #1 goes high, then the dummy signal will be routed by CobraNet to PS8810 #2. A Noise Gate in the PS8810 #2 will go off and this will be diplayed at the control port.
2) you could contact me in Heilbronn.

Best Regards,
Audio Pro Heilbronn
Dirk Hartmann