+2 for Phil's summary.
I own the FA84 in the 184 length. It is a LOT of ski, really coming awake somewhere around 35 mph. Below that, it works fine, but feels dull, and almost "bored". I cannot remotely find its speed limit, and will just say that 58 mph is not it. Off-piste, it is demanding, and in bumps it's kind of looking for the exit.
I'm typically a lover of Nordica skis, having owned several -- and the FA80 may be my all-time favorite do-everything ski -- but I am probably going to sell the 84s. They are a strange ski, being a bit wide-waisted, but almost completely front side oriented. In that environment, I have more fun on my Blizzard G-Force Supersonics with their 74 or 72 waist anyway.