Actually going from 6" to 4" is only a 33% decrease in your theoretical max speed. Going from 4" to 6" is a 50% increase. If you dropped from 4" to 3" it would be a 25% reduction from where you are now with an expected max speed of ~28 MPH at 10k RPM. This doesn't count for inefficiencies and the general rule that nothing ever works as well as we plan... . Also, this assumes level flight, not speed during or after a dive.

With a 3" pitch prop and a 10 MPH headwind, you might be able to outrun your airplane.

If you want to predict the max speed for a pitch use this equation:

( RPM * 60 * pitch in inches)/63360=MPH.

Someone feel free to correct me if I'm wrong; this has happened many times before.

As for the Byron, I think it's cool too... unfortunately, I cannot take any credit for it. It was built by a guy in our club who sold it to me at a recent swap meet.

Have fun,
Scott.