Tried a 21x10 today. Outside temp was 11 celsius, so had pretty good air. 6300 rpm, 25% coolpower, didn't really play with the needle, just got decent smoke, to cold to fool around for me. Anyways I absolutely loved this prop. Pulled verticle forever and downline breaking is really good, you need to be throttling up before you pull out, flying ama masters. I was able to get a more constant speed throughout the pattern as compared to when I was trying the 20.25 x 10. I really liked it. 13+ minutes on 20oz tank.