I started breaking in a new Saito 1.00 today with a 15x8. I know things are still running pretty rich, but the best I could hit was 8800 rpm. Plus I'm at 5200 ft. above sea level. 15x6 is in the range of props for this engine, so go with it if it flies the plane. You'll have better throttle control with the 15x6. More speed with a 15x8. The more you run the Saito, the better it will run. Don't forget to set the top end a little rich on your final setting. Max rpm then richen to drop about 200-300 rpm.

Mike