Have you gotten Thrust HP from the RCFAQ page? I love this program. I just looked at the Brison 2.4 RPM data on the RCFAQ RPM database and there are only two samples for the 20x8 and NONE for the other props you mention. It is apples and oranges, but I am spinning the 19x8 Mejzlik on my MOKI and I REALLY like the performance. It slows down just fine, to the point of having to ADD throttle to crawl it into a landing.

I sure like this airplane, in some ways better than my BME 44 powered Dave Patrick Extra. It is very very "smooooooov" .

-Cheech