Then, if the F4U-4C didn't see service in WWII, our F4U-4 shouldn't be perked.
Seriously, it out-performs the P-51D, but not enough to warrant a perk price.
And I think that the F4U-1C should have a default perk price of 5, since it's an F4U-1 with 4 20's (and a nicer cockpit).