Larry,

What RPM are you set at and what length lines?  What is your desired lap time?  10,300 RPM seemed to be the starting point for this prop.  That acheived a 5.4 lap time on the Strega @ 79 ozs and 66' eye to eye 0.018" lines.  This also worked for the Pathfinder with the prop cut down to 12" using the same lines. 

The purpose of this prop was to get the rpm's up to get the motor in more of a sweet spot (70-93% throttle on the Phoenix) and to increase the resolution of the governor by making any change in RPM have less effect.  I think that once you have your RPM set, you will like the lower pitch better.  If you try the ful 13" versus the 12" on the same airframe, you will have to be higher on the rpm for the 12" than the 13" by nature of the increase in thrust with the larger diameter.

Archie Adamisin
Muncie, Indiana 

I think my lst flight was at 10,400 in St. Louis.  Yup a good prop.