Southerntouch said all when he gave you the pitch on his 12" prop. A combination of diameter and pitch is what feeds the bulldog. A larger diameter and lower pitch prop will give you more RPM and increase your climb rate in most cases. If you're a full size airplane driver you know that the prop goes into low pitch for high RPM on take off and landing in case of a go around. Higher pitch is for cruise when used in conjunction with the manifold pressure guage, outside air temp and tach. If you want more vertical performance go for the lower pitch. If you want speed around the pylons high pitch will do it. We have some people that us 10 X 8 and 9 for pylons with a .46