Try this:
Mac master ethernet 1: 192.168.2.1
Mac master ethernet 2: 192.168.3.1
PC Slave 1: 192.168.2.2
PC slave 2: 192.168.3.2
The 3rd field of the static IP address designates the network. The 4th field is for different machines on a network.
edit: stay away from 192.168.1.xxx. The "1" network will have all the dynamic IP's for your various devices.