If you are getting 5 out of 10 top end calves with ANY breed from only 10 cows you are in the upper 1% of this industry. I don't care whether you're breeding clubbies or the most consistant purebreds out there, you don't hit a home run every time you put in a straw of semen, if you did we would all be rich, if most of us get 2 top end calves out of 10 you're doing great and it has nothing to do with carrier status.
Jeff_Schroeder-PHA has been around for 30 years, I guess I'm missing how you think it spread so quickly? Sorry to modify, but I wanted to add to this, some of the most maternal sires in the Maine breed are PHA+ and I would say that had more to do with them being used heavily than for the bone and mass, Draft Pick, Irish Whiskey etc are used to produce heifer/cows more so than the bull counterparts, if the big + for PHA is muscle mass in my mind it would be the other way around.