Well, Most people i know fly ybs on darkness, Early bred ybs at that too. With doing this they have had great results. So your opinion of early bred ybs comes down to money and thats it. As for loses with ybs, It's not about when they was bred, if they was on darkness and whatever, It all boils down to schooling, If a yb is well trained, and fit and healthy you shouldn't go far wrong with it. Last year i bred 50 ybs, had a shocking yb toss which ended up me loosing one yb. I flew the entire yb season, Disposed of a few and still had 41 in loft at the end of the racing season. They was on darkness and it helped them. 2010, I wasn't on darkness, they didn't want to know about racing half of them couldn't compeat with they fully feathered darkness young birds which other club members was flying.