Well I believe I've received the answer to my question because apparently no one has experienced a 3 blade prop reducing P-effect. At least no one on this forum. In fact no one suggested any benefits of a three blade. Guess I'll save $200.
Jim O
I just maidened my Caelus #2 today. It has a 22X12 carbon 2 blade prop. My competition plane (Caelus #1) has a 19.5X13 carbon 3 blade. Other than the props, they are identical in every way, from c/g to wing incidence. Both planes require working the rudder on up-lines. So...no difference as far as I can tell. BUT the 3 blade has a much more consistent speed envelope, both under power and off-power down-lines. Also, the 3 blade sounds much better.