TonyJoey was the last guy to get the #1 fighter rank in a P51 a couple of tours back. He hasn't played since then and no other 51 guys have stood out...at least that I've seen. In the past there has been Grmreaper, Steve, OlDemon, SkatSr, Tango, Nigtmyr, and Pand. KrapShot was good, Paladin is okay but could be more aggressive, HighEye tries but lacks the gunnery to get out of bad situations.
But what I find interesting is most of the really good pilots in the game don't fly the 51. If Kappa, or Bruv (for example) chose to fly the pony exclusively they would be top pony dawg.
Also I remember Seano to be a handful in a 51. RedTop and AKDG too.