Perking the SPIT XIV is fine because of the spit fetish of the main and it turns pretty well for a high performance fighter. It also outclimbs EVERYTHING in the main. Granted the perks are too many 20 should be fine maybe even 15 but not 60.
The Dora and 51 should remain the same because The P-51 is great but doesn't hold all the cards that warrant a perk and the Dora has a good climb rate but not the best, La-7 is faster then it on teh deck, P-51 both outruns it and outclimbs it at alt it doesn't turn well. Really it's just a fast plane that's good at E and BnZ fighting but get a plane that's faster than it and it's kinda screwed. The Bf-109G10 should remain free too, it doesn't turn that well it's guns aren't the greatest (unless you want to lose performance) and it is pretty weak armor wise.
The Spit XIV is obviously much better then all of the above planes except for some of the speed category.
BTW, I was wondering what's the figures of the Spit IX (you claim it's a 1942 model but what model is it called?) to the SPIT IX LF that you all say you want so much?
Maybe that could be added to appease the Spit Flyers while the Spit XIV could be a 20 perk plane that is an incentive to work for

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I'm always working towards more perks to fly the 262 more often

Also, that post I made about the more skilled LW pilot blah blah blah... What I meant is the reason teh K/D ratio of the Spit 9 or P-51 isn't that high is because a lot of people who are new hear the Spit 9 is easy to fly or they like the P-51 cause they're American and they've heard a lot about it and stuff like that. Think about it, most newbies aren't that concerned with flying the Dora. I actually find the Dora a little difficult to get a good gunnery solution on due to it's lower velocity cannons and MGs plus the fact that the big nose obstructs the few in high angle off shots.