When 4G Transceivers get configured in the right way, that they end up with the corresponding SFP+ parameters, a warm welcome message is sent to the 4G SFPs by Brocade Host. Then there is nothing standing in the way of the 4G FC application so it works. The Pin configuration (SFP to SFP+) differs only marginally although it does not affect its proper functioning. I suspect that this modification does not only work in Brocade 6505s. In my opinion, this should also work in 6510s and 6520s. I look forward to receiving your feedback on the above.
For the configuration modification we have created a special template which can be found on reconfigure.me. For our 4G 18dB CWDM (S.1648.18.xD) this is already available online. Enjoy it.