I think number 5. Just about explains it all, AT LOW ALTITUDE, I have never seen any dogfights on IL-2 that take place at about more that 5000ft. But why is also the Spitfire so Spinny? Maybe the Western planes are not as good but they certainly knocked down their performance a bit, I have the same problem with 1946, Get the flight 1 P-51 for FSX (Thats how a pony Handles!) Then fly the one on 46'.
Until you do that you will not see I am getting at, and don't call the Flight 1 addons Innacurate, they had access to two Real FLYING P-51's, that I had the fortune to sit in...
Regards,

Jack