Tumor, read six posts up from your last post.
The two lengthy posts are entirely about the Spit9. Considerations and still more considerations, and yet, still the Spit9 fills none of the major categories I've considered for the perk candidates. That's why it's always a dilemma

And no, Karnak, it isn't based purely on date - technically, the reason it has a rounded out exterior of about 1943, is because all the planes after 1944 in AH breach either one, two, or all of the major aspects requiring perk in my opinion - performance, rarity and multi-role aspect.
Usually those aspects are interlinked - in the case of most of the late war planes, they came out after 1944, which means:
1) they are most usually very high performance
2) some of them are rare
3) they developed multi-role aspects
So, very naturally, the planes before that era lack most of those three aspects - relative high performance planes exist, but none of them are like the La-7.
The problem is, the Spit9 fits into none of the three reasons given which effect people's choice on planes, and yet, it holds 10%. The sole reason for its success is balance of maneuverability and speed like no other plane except the N1K2 - their maneuverability is excellent, and they are very fast, compared to the handful of planes that turn even better then they.
Frankly, that translates into "easy plane to fly and fight in", "easy mode" if you will - regardless of actual effectivity or impact.
Most Spits and N1K2s form the 'grunts' of the MA forces, fighting the highly risky and dirty battles where survivability is hardly expected. They usually are ignored by fast planes, and usually fight the same types used by other countries on deck. Simply put, its a plane loved by dweebs. No need for understanding in real ACM, no need for careful E management, just fly, point, fire, then get shot down.
...
But the problem is, perking a 1942 plane for the reason it is a good balanced plane, which is not a super plane like the La-7, doesn't make sense. It sees heavy use by all kinds of people, and for one thing, the dedicated RAF fans will never ever understand that. The N1K2 is a quad-cannon plane with 900 rounds, a relatively rare plane, and also a 1945 model. At least the N1K2 got reasonable grounds to limit it.
And that's what I was trying to figure out 6 posts above - what will happen when the Spit9 is alone, among the big four, left unperked.
Since all of the suggested perks aren't really penalizing, maybe there can be a compromise to perk the Spit9 even lower than most planes, maybe 2 points - just to make average pilots who have to really concentrate to earn 3~4 perks in an hour, so that they think twice about the 'dweebing'. But as I said above, it's a path I'd like to stay away from...