For speed, you need RPM and pitch. You'll go with a lower-diameter prop and a higher pitch. This will lengthen takeoff runs and hurt climbout. As far as the SuperTigre G90 is concerned, we really don't have information for you. We haven't used a pipe, and we don't turn it over the mid-12,000's. The engine isn't really intended for speed. If it's run in the low 13's, it should hold up OK, but make sure you have excellent lubrication...your fuel should have a significant amount of castor as part of the oil package, and total oil should exceed 20%. 'Tigres have always done better with higher-oil fuels containing castor. That's how they were designed.