for the 207 you need the "VELA"version of firmware. which can be downloaded from the support site.
I noticed today not every release is available for the VELA (207) version.
browsing throug the version list, i found 6.5.4.0 (latest) to be available (please beware, airwave strugles whith this version :))
6.5.1.x seems to be the "first" VELA version
https://support.arubanetworks.com/DownloadSoftware/tabid/75/DMXModule/510/EntryId/26265/Default.aspx