I'm flying an Extreme Flight Yak 54, (the 68" version), with one and I am having very good luck with it. It is very important that if you are using a Pitts style muffler that you plug one of the outlets. If you read the tech notes on Tower it states this as well. I am running an 18X8 prop and it has PLENTY of power. I fly at 2800 ft. ASL and 5800 ft. ASL, (depending on the weather), and the engine is easy to tune and maintain at both elevations. You may notice a little more vibration with this motor, (all my Super Tigre's have a little vibration), but all in all I feel it is worth it. I figured it was better to put a little more money into better servos than pay $300 to $400 for a comparable powered engine.

T.

P.S. I hope the YS guys don't spit on me for this...