I recently saw an article where they took Pro Zinger, and cleaned up the design. The RPM it turned, dropped, but the thrust went up. Everyone puts so much emphasis on the RPM of a given pitch and diameter. The PLF really muddies these waters. I am guessing that prop composition is one of those variables Pe Reivers is talking about. It sounds like experimentation is still the best bet. That was easy, when I was running .40 -.91 sized engines. When I moved up to 40-50CC engines, experimentation got expensive. I can't imagine the cost with the real big props.

Thanks for all the input guy's! Your experience is priceless. I don't always understand everything I read, but as time goes on, more and more of it makes sense!