I thought gaining advantage from any other grade was grounds fer disqualification...
I was working with another bloke to pull in the break yesterday, we caught a pair of C graders (at the crest of a hill) and for a brief time all 4 of us drafted down the hill... then one of the C graders (who was behind me) pipes up with "you're not allowed to sit on his wheel"
I apologised, but fer feck's sake I was just after a rest... I had to drag my brakes to stay behind him, hardly gaining advantage.

So we promptly dropped them