What FEC (Forward Error Correction) rate does the FG6501Fs support

As best I can tell, from their minimal documentation, is it sends additional packets with some form of checksum data which allows the other end of a VPN tunnel to recreate lost packets on its own rather than the IP layer apps having to request a retransmit.  So, you may achieve more predictable performance (lower jitter / loss / retransmit) and possibly even higher overall throughput (on a lossy link), at the expense of sending more overall data.