On the issue of Japanese aircraft speed.
1)Historical part. As a preface, I'm not a big fan of counting precise speed numbers. Max speed squeezed out in optimal conditions and often on a specially fine-tuned airframe does not tell the whole picture at best and can be outright misleading at worst (for a Pacific-neutral example - MiG-1/MiG-3). Unless one does research in depth, evaluation by those who operated planes in the field (with opinions from both sides when possible and taking things like survivor bias into account) and combat results, when there is enough data on outcomes of individual clashes, are preferable. I'm focusing on speed here only because in the game max speed is a vital statistic, possibly the most vital in the air combat calculations.
It is also not news, that commonly accepted performance figures can wildly deviate from reality, because of unaccounted for difference in testing methods and other factors. As another neutral example, max roaspeed of Pz.III is almost always stated as 40 km/h... except that its normal driving speed on an road. When tested for maximum speed in USSR, a captured early Pz.III demonstrated about 68 km/h, outracing every pre-war Soviet tank. In case of aircraft even stuff like painting on the day of trials might impact the results.
Now, returning to the Pacific, there are solid reasons to believe that maximum speeds for Japanese aircraft, as stated by Francillion and copied everywhere else, are systematically underrated. Which is vital, because speed differences that were barely noticeable IRL might mean alot in AE. For example, look at the analysis of A6M2's performance:
It might hint at one of the possible causes of this underrating - providing figures for the military power equivalent, rather than for war emergency power equivalent. For other aircraft, other reasons might exist (for example, Ki-84 underwent an engine update without a change in model designation during the war, so data for 1943 prototype tests is not likely to be valid for late war).
Talking about George, if you look at p.64 of "Genda's Blade", you can see that American wartime estimates credited N1K1-J with 407 mph. See also:
Considering that F6F has noticeably worse power loading and is not that smooth aerodynamically too, this makes sense. This is what I was using as a benchmark.
In terms of AE mechanics I find Hellcat not the deathmachine it was in reality, but a poor relative in the family of the third-generation Allied fighters. That because its relatively poor speed is not compensated by maneurability or survivability (again, compared to other Allied fighters) and, again, the game values speed perhaps too much. I tried to fix that in the last version of Scen 70, so comments from John, who plays it and should be in the Hellcat age by now and should have some experience about them, are much appreciated.
However, this out of the way, I see validity in your complaint, kfsgo. If Allies totally cannot rely on fighters weaker than Corsair/Lightning (both of which have reliability problems throughout 1943), which might be the case with George's stats like I proposed above, and only have qualitative superiority with Thunderbolt (which probably will be available 2-3 months after Shiden, and in lesser numbers), they will be in quite a difficult situation in 1943. So, after such a long post explaining my motives, I have to admit, that in general you are right, and at least N1K1-J needs toning down by about 15-20 mph, others probably by 10.
Yeah, I just get snickety since I spend too much time messing around in IL-2, really (so the MiG-3 comment resonates...christ, that thing's painful), and so that colours the way I look at the things themselves perhaps more than WITP does. Of course, IL-2 being what it is you're a) at the whim of whatever weirdo modder edited the aircraft this week and b) sort of left thinking "woah, there's a fighter you can get over 350mph? that's a first...". So, it's not proof of anything, just somewhere to start. I mean, ultimately, I'm not a pilot - any argument I make on the precise details of this or that aircraft feature are basically from a fairly ignorant starting point, and I try to remain mindful of that when talking about this stuff.
That said, I would guess that issue, fundamentally, is that although we have variable maneuverability for particular altitudes we don't (as far as I know) have variable maneuverability for particular speeds. To go back to the IL-2 thing - one of the most hilarious things you can do in IL-2 is get a P-40 going fast; whatever faults it may have maneuverability-wise when slow at sea level it's a fantastic aircraft to toss around at high speed, and you can run rings around the contemporary Japanese stable in that situation as their elevator and aileron control go to pieces once you get them going fast - all that emphasis on light weight has consequences, in the end; probably similar principles would apply when considering the "poor" performance of the Wildcat in-game. I would suspect this to be an issue persisting through the N1K (2.5t) vs. F6F (4t+); your forum report suggests aileron dropoff on N1K around 360mph, which I would guess (without any proof) is lower than would be experienced on F6F. So, I guess the question becomes - do you want higher speeds, or higher maneuverability; you can have one or the other, with one eye on the way the game models aircraft, but not really both.