sydclement man I belive you. Thumbs up for the 200+ flight!
I cant seem to rely on the rpms with prop selection for the top speed theory. there are so many other variables out there to consider. Aerodynamics, tail wind speed when in dive. I don't think just because it tacs on their ground at a certain rpm that it will not go any faster than that.
For example: I also fly Buckeye powered parachutes and the posted top speed was 30 mph. With a GPS and flying right over a truck it flew 45 with tail wind. Even though the prop and rpm may of been 30 mph top speed on paper. This was while running 6500 rpm. So rpm and props may have an idea on speed but you cant just rely on that to achieve a high speed.
http://www.buckeyepoweredparachutes.com/582dm.htm