i messed around with the recommended breakin prop on my 30, and felt it was a bit small...I have my 30 on a 1/4 H9 Cub and experimented with props, and IMO my fave prop is a Xoar 19x6, even though the 18x10 mejzlik looked awesome on her.. i get about 80-8100K rpm which is about right for the engine