mesa 7i74 ModBus capable channels?

Hi all,
I am trying to use the 7i74 for interfacing the ModBus functionality on 5 servo drives and I just realized that in the manual it says only channel 7 can be used for RS-485. Is there a way I could use the RS-422 for ModBus or would I have to get a different daughtercard for my 7i76E to get more RS-485 channels?

1. Normally just one RS-485 channel is used for multiple devices (multidrop)
2. There is no current support for ModBus via the Mesa UARTs so typically this is done from the host PC with RS-232 to RS-485 or USB to RS-485 adapter

I was going to try writing a modbus driver for the Mesa UART. There is support for sending and receiving in the hostmot2 driver. See this post.
forum.linuxcnc.org/27-driver-boards/3328...mesa-7i76e-with-uart