450 on the deck?
Your kidding of course, a Tempest in full WEP does 375 on the deck.
The FB VI did @ 380 tops clean, and @ 335ish on the deck. Its not a jet.
...I like the Mossie FB VI and have done a few tours in it as my main ride. For starters, dont roll it with too much fuel, 25 and DTs or 50 internal max, and pick your fights, keep your E up. Its not a single engined day fighter so dont expect too much out of it. It turns a nice corner, and it has awesome firepower, but like any type it has its drawbacks. Make sure you fly it at its best alts.