Pairing for natural ybs

I know it's to late for this year, but when would you guys pair up your stock/race team for racing natural ybs, Luke and myself are trying darkness for the first time ,and, we were warned, that it is pretty time consuming, and so far that's true, although some of the birds are looking the dogs danglies, just sort of thinking ahead to next year (shows how bored I am)and was wondering about the old darkies v natural scenario

Forgot to mention our first yb race is around the middle of july

naturals wont keep up with darkies they may for first few races ...racing natural ybs I would pair early march so their coming away from the nest end of april early may