Thanks Ace, it's good that you arrived when you did. Though you have proven our figures wrong, I think the three of us can agree that our BoP planes are much too slow at least at sea level.
The Spitfire IX in-game has a larger rudder, suggesting it's a late-built model, most of which were equipped with the Merlin 66 engine. Spitfire LF IX (one's with the Merlin 66) could usually pass 330 mph at sea level. You'll notice that isn't anywhere near possible in BoP. If our Mk.IX is indeed modeled after the first Mk.IX's that entered service with the Merlin 61 in 1942, I should still have little problem passing at the VERY least 310 mph without WEP, which again, does not happen. Of course, since all the planes are a little too slow, that shouldnt be much of a problem. The problem arises when the Hurricane behind you reaches 200 mph the same time as your Spitfire IX when you both started at 170 mph.
Acceleration is a very important advantage that some fighters have over others that simply allows for a domnant energy fight.
kozzm0, Lift cannot be produced without drag. When the slats are deployed, they do indeed produce much drag, but that's not a problem when you're pulling alpha trying to out turn someone.