Using an old rule of thumb, you can double the diameter, and add the pitch, to campare props. So if you cut down your 8.5x9 to 7.75, you would be just a little more load than the 7x10. McCoy's are luggers, so the 8.5x9 might work just like it is. I run 10x6's on mine in stunt, and that would be the same load as your 8.5x9.