I did read that somewhere, that the 9t pinions are likely to crack. I’ve seen it a couple places. I’ll go with the 10t. It’ll be more headspeed and I won’t have to worry about a crack. The 9t pinion would have had real low headspeed, which is what I wanted, because I’m just doing forward flight. But if the 9t pinions crack then a 10t pinion would be better and not too much more headspeed then the 9t