Yes, go with 4.0 or higher.  Once you start to purchase M5 blades you will need 4.0x or higher. JB

James, I think we some more detail on what FI's you have and what hardware are you running?  How old are the blades and what models and long with your FI's?  EOL 6120XP's are stuck at 2.2(8) and I am assuming you are at least using 6248s or newer.  A...