Hello,
the FlexFabric Adapter is supported in a BL460cGen8 Server. If your Blade has a lower Generation Number it will not work.
Please provice more details about your Blade server, Partnumber would be nice.
Both Onboard NICs are mapped to Bay1. The first Mezzanine Card will go to Bay2 and the second Mezzanine Card goes to Bay 3 + 4.
Thomas