maxprop pitch

a recent post inquired about setting the pitch on a maxprop. i
reviewed the installation/owner’s manual- what you set is the angle of
the blades. of interest to us, for a 16" prop, an 18 degree angle
gives a pitch of 9.8, 20 yields 11.0 pitch and 22 degrees results in a
pitch of 12.2 inches. i have mine at 11, 12.2 was too much and i
believe that 9.8 would be greatly underpitched.
john churchill