How many PLC Controller Types can exist under a PLC Generic Control Network?

Hi,

I want to use Compact HMI 5.1 FP4 for communicating modbus serial slave devices over ethernet (Converted to Modbus TCP using the serial to ethernet gateway). In CHMI I found that each slave device needs to be configured as a PLC Controller Type. My concern is I have to communicate with around 300+ devices. How many PLC Controller Types can be created under one PLC Generic Control Network? Can I have multiple PLC Generic Control Network objects in control structure CHMI?

Thanks in advance.