Thats nonsense, Vinky.
Speed: yes, its the fastest propeller-driven aircraft from 8-27K, has a long wep. But on the deck, the F4U series, 190D, Tiphy, Tempy, La, Spit14, M-jug are all faster. Its still very quick, but not the top 1%, not nearly.
Climb rate: its really top notch, insanely quick all the way.
Acceleration: made some test with Krupinski, the K4 accelerates very well, but far from the top 1%.
Firepower: while its one hit - one kill, the ammo load is small, and any fighter further than 400 is practically untouchable. A mixed bag.
Visibility: very good - for being a razorback birdcage. Otherwise, poor.
Roll rate: medicore from 150-350mph, practically non-existent over 430. Aileron rolls cant really be performed near the stall, due to the strong torque, but the snaprolls are easy and steady. A mixed bag, again.
Flat turn rate: ~19.2 seconds per circle, on the deck. Thats poor, considering the spit8/9/16 turns around in 15-16 seconds, the spit14 in 17.5 seconds, the lala/p38 in 18.3 seconds, and the 190D in 20.5 seconds.
Flat furn radius: large, ~535 feet with full flaps, according to DocGonzo's site. Thats about the same as the Spit14, P38, 190A5, or the P47D11 with the small gun package.
Low speed handling: i was fammiliar with this aircraft, felt it quite handy and forgiving, both on the edge of stall and in the post-stall moves.
In a hands of a dweeb, the K4 can escape from the fight quickly. Isnt the best horde-munkey plane as it cant really dive and cant get a kill from 600. But when a veteran is flying it, it turns into a beast, being able to stay with the stallfighters for a while or overshoot them and shoot their donut with the tater - just whatch RedBull flying it, or anyone from the same category. A truly impressive sight, yet very difficult to get the most out from this aircraft.