If you want speed then you need a smaller diameter, higher pitch prop. I have flown this plane with 12x10W APC prop on an OS 91 with good results. You will need to get your idle down good and low or it will land fast. This is a great airplane and a knock off of the Goldberg Chipmunk and both fly extremely well. I currently am flying mine with a Saito 1.00 and a 14x8 prop with good speed and vertical performance. Whatever prop you choose, keep the tach reading up in the mid 9000 range.