Keep your circle tight and your dogs tight and hear say wont enter the equation. You wouldn't need to rely on it.Theres probably 2 or 3 fellas in the country who's word I would take for gospel no questions asked. If they said a dog was doing it then that dog was doing the business. My dogs go back to some of the fore mentioned dogs and are now throwing a greater number of workers than ever before but believe me I've bred some useless dogs too some of which would really have you scratching your head but every one does. Sometimes the mating just doesn't click even within a line. Just cut that branch off and get back to your main stem and go again. Unfortunately luck does have it's part to play I reckon but so too does giving a dog time to mature . The best possible lines even have there skeletons in the closet guaranteed.