Look I don't believe in that way less efficent stuff. If they are so inefficent why are dropped down 1 size and 1 pitch. Use the dubro pointed colored aluminum spinners and a 9x6 or 9x7 3 blade and go fly. You'll have good RPM and at 1/2 to 3/4 throttle they will have great effincency. OH by the way don't tell your engine he's 3 bladed , CAUSE HE WON"T KNOW THAT, THEY will love those props. 9x7 will be a little bit better than 9x6