ACF...on the high pitch recommendation I think you might be confusing your 91 CD with the 90 SP. They are completely different because the 90 SP has a 2:1 gear ratio, so it turns 5000 rpm where a normal four stroke turns 10,000. That's the reason for the higher pitch recommendation. But it applies ONLY to the SP series (60, 90, 120). So if your engine is a 91 CD, then it doesn't need any higher pitch than any other four stroke.

Going with a lot of pitch might not be a good idea on your plane/engine combination. I'm guessing you might want good low speed thrust for safe takeoff, but I don't know the plane.

There is a big controversy on another forum about the efficiency, or lack thereof, of three bladed props vs two bladed props. Passions run high on this subject! You will find lots of people insisting their 3 bladed props do just fine or better than 2 bladed.

I think it comes down to the match between motor, prop and airframe. If it's a good match, people like the prop, whether it has two blades or three.

Jim