adding a shelf to an AFF220

Hi All,

We have an AFF220 with one external shelf and are adding a second shelf. 
I see clear info in the NetApp docs on how to connect multiple shelves, 
daisy chaining the shelves and returning the last shelf to the head.

But the docs are based on setting up a new system and I haven't found 
anything on adding a shelf to a new system. Do I just move that return 
cable to the new shelf? Will there be any interruption to services? What 
else do I need to know?

Thanks,

Randy in Seattle