I am brand new at pattern, currently learning to fly the Sportsman routine with my Extra 330S (67"/8.5lbs). I am using an OS 65 LA with a 13-6 APC prop. Measured RPM and thrust are 11,300 and 8 1/4 lbs respectively (this amount of thrust really surprised me!). Also, I am using a Bison Pitts style muffler. Needless to say, the power is more than enough for the Sportsman routine. But ...... , I just had to try a 12-10 APC pattern prop to see what this will do to the flying characteristics of the plane. Being fairly well versed in aerodynamics and such, I would think the plane will fly faster, but pull vertical less smartly. A new pattern friend of mine has a 12-10 on a Webra 60 in a Kaos with pipe. His plane does the Masters pattern beautifully. I don't understand (he doesn't either. He says it just works!). With this prop the RPM and thrust are 9,300 and 6 1/4 lbs. Also, things are a lot quieter (by my ear, not measured). I haven't flown this new prop yet due to high winds which should go away tomorrow. I thought it would be interesting to hear peoples opinions on what is going to happen when I fly the plane through the routine, and maybe an explanation as to why. In a car when I want to go up a hill I down shift ( less pitch, higher RPM). That I understand. One last thing, 9300 is right at peak torque for the 65 LA.