Prop chart...
"http://jimsrc.com/jpg/tech_propchartws.JPG"
Interesting prop chart, however it is tuned for sport flying not max speed. A 7.4x8.0 prop now running on Nelsons is recommended for .10 to .15 engines! Recommended prop for a .40 engine is 10x5 to 11x6.
These are not go-fast props.
Stan D.