Pakrat you were fairly correct about the Yakovlev series maneuverability. They were among those FM's I modeled based on Power OFF stall speed data. This has been fixed now with update FL2054 (see separate post for details), and the Yakovlevs now stall at an ~8 mph IAS lower speed, meaning they can turn and maneuver better. They will still not flip like A6M Zeros but are definitely more competitive than before.
The new Yak-9U flightmodel is now finished and waiting to be released. This Yakovlev version has a much improved max dive speed (447 mph) compared to the older Yak's (404 mph). Also due to Frise type ailerons it retains it's roll rate better at higher speeds. Service ceiling is 35000 ft and it is 168 lb heavier than the Yak-9D and 1094 lb heavier than the Yak-3 (which had smaller wings though). Maximum speed is 366 mph at S.L. and 414 mph at 16400 ft, which is very close to the numbers in the Russian Yak-9U Pilot Handbook (366 and 410 mph). Other Russian tests claim 359-363 mph at S.L. and 418 mph at 16400 ft. It is also better than the other two Yak's in a sustained turn due to it's improved power/weight ratio.
Below is a comparison of the Yakovlev models vs the P-51D and new Spitfires (which will soon be released fully remodeled in the coming FL2055 update).


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/Robert