Class A, B, C and D would never fly, especially at the federal level. Would have to be AAAA, AAA, AA and A to be "proper". Don't laugh; high school sports classification in my state used to be AAA, AA, A, B, C and D when I played (1960s). Now they are AAAAAAA, AAAAAA, AAAAA, AAAA, AAA, AA, and A.
Ted, KX4OM