Can you manually configure the Channel on a ePMP radio?

Answer: Channels can be configured via the GUI under the Configure --> Radio menu.  On the AP a country code, channel bandwidth, and frequency can be selected.

For the Station, preferred APs can be specified for association or the Station can be configured to associate to any AP with best receive performance.  The Station can be configured to specify which channels and bandwidths to use to search for APs.