Oh heck, no lower than A. But I'm sure I missing several others that are or were just as good. No doubt Grizz was good, but most the time I seen him it was in a 262. CorkyJr on the other hand did his stuff in a 38G. I always had it in my mind for some reason that the best pilot in the game was either a 38 or 109 flyer, because of the skill it takes to be good in them.
Guys that fly F6Fs all the time seem to really be good dogfighters too imo.
I'm just getting back into the game again and dont know who knows what just yet. But from what I see, about everyone I've ran into is at least a B. The one thing this game don't lack is good dogfighters.