It's been quite many updates since the last version I've tested, which I'm pretty much confident to say quite thoroughly and accurately.
Under the premise that those many updates did not fundamentally change each and every plane in its flight characteristics so far as to produce individual results that are drastically incompatible between each versions, I can vouch for the P-38 that there's nothing wrong with how its flaps effect combat flight.
Under my tesitngs, I was quite surprised to find out and confirm, that the AH P-38J and L variants were one of the worst maneuvering planes in terms of turning radius - with or without flaps, which is pretty much spot on with historical accounts - at least, with some sources such as described in the commentaries and excerpts of <America's Hundred Thousand> et al..
The empirical disparity between its perceived performance inside the MA, and its actual turning radius under controlled circumstances, is a very compelling evidence that the P-38 in AH, in theory, shows unique strengths which allows it to overcome its poor turning radius - namely, a torqueless platform that boasts very high levels of stability than compared to a normal, single-engined aircraft.
It's not that the P-38 turns better than others with/without flaps
per se - but rather, the torqueless/stable nature of the P-38 platform allows it to dump speed and enter minimized, tight turns quicker than any other single-engined aircraft.
A normal aircraft - despite its lighter, and more maneuverable envelope - must often struggle to maintain critical balance to sufficiently lose speed and enter very tight turns, and must keep on struggling against imminent effects of violent destabilization at those speeds (particularly in the roll axis) to maintain the radius, whereas the P-38, in a sense, can safely enter a turn and keep tightening its radius without any delay.
Most often, this difference manifests in the MA in the form of a fight that begins with the P-38 on initial offensive, and the pilot on the defensive finds himself in a puzzling situation where no matter how hard he tries to outturn the P-38 behing him (which should supposedly be unable to match his own turn radius), the P-38 just cannot be shaken off.
What happens, is that in the initial stages of this battle, the P-38 behind the defending aircraft slows down a lot faster, and thus, gains a firing solution. Even after the fight devolves into a slow-speed turn contest (provided the P-38 has failed to shoot down the defending aircraft in the initial stage of the battle), the defending plane struggles throughout the many circles to keep his plane from destabilizing and spinning out on the roll axis, and at the same time trying to tighten his turn more and moe - whereas the P-38 behind him with flaps out, more or less comfortably maintains perfect balance throughout the circles and still maintains a firing solution.
It is only when the P-38 fails to shoot down the defending aircraft in the above two stages of the battle, that the "real" difference in the turning radius starts to kick in, and the P-38 finally starts losing ground in the turning contest.
I've often met similar circumstances when flying in the Ki-84, a very powerful, maneuverable plane that is capable of outturning most Spitfires and matching the Spit5 in turning radius - against a P-38.
Because the Ki-84 (despite being a single-engined aircraft) has the same type of efficient flap configuration as the P-38, it flies very similarly to the P-38, at least, in horizontal turns. As long as you can dump speed quickly enough to pull out the flaps, the Ki-84 can maintain an incredibly tight turn radius and chug through turns cleanly and stably at imminent stall speeds.
This makes the Ki-84 a very good match against the P-38, and often a turning contest lasts many circles, until finally, the P-38 losesconsiderable momentum, and reaches dangerously low speeds - at which point, the superior turning capability of the Ki-84 finally starts to show advantage, and decisively outturn the P-38 in the horizontal.
This is very impressive on the part of the P-38, considering the fact that its true turn radius simply is no match for the Ki-84. Despite this difference, even the Ki-84 needs a lot of time to finally win the low-speed, super tight turning contest against a P-38.
