For what its worth, I think we've got enough grades but they could be tweaked.
My opinion is that AA should be above 90%.
It should be an 'elite' division and it should be bloody hard to get into it.
Maybe it should be easy to be promoted but much harder to be demoted?
I'm thinking of guys who, quite rightly, enter C grade at the beginning of the season, but it is quickly obvious that they are much better than a C grader.
How about in B and C, 2 consecutive scores that are more than a grade above your own automatically promotes you a grade?
But you are only demoted after all the GP's?
And I would only count BFTA events for grade score.