This should work.
I don't have a multibay enclosure, but have had 3 hard drives connected via a powered USB hub to the AirPort Extreme with no problems in the past.
I'm not sure if you are planning to use Time Machine for backups, but if you are....you should know that Apple does not support this type of configuration.
It might work, or you might have issues. Bottom line is that it is not a reliable method for Time Machine backups.
Currently Being ModeratedNov 24, 2011 11:37 AM (in response to Bob Timmons)
While I was not planning to use the HDDs for Time Machine, it's good to know that is not a supported function.
Is any of the HDDs connected to your Airport Extreme larger than 2 TB?