Adding another 220 Pro to make 440 Pro

[sfdude]

I'll be taking possession shortly of a second 220 unit to make a 440 Pro CI set.

Couple of questions: 

1) I'll have 2 remotes. Will both remotes work on my system?
2) Will I need to have both units with SD cards of the configuration file or just use the SD card in the Master unit and leave the Slave unit with an empty SD slot?

Thanks!