I run an OS 46 AX in my WM Ultimate 40s . Like the last post stated, I placed the battery under the canopy which made the CG perfect with the 46 size engine. I have read several posts where builders are running fairly large engines like the 82 four strokes and I'm a believer in having plenty of power, however, this plane performs great with a 46 two stroke. I selected the OS 46 AX because I've been using one in my Hangar 9 twist for the past year and it has not missed a beat. Its small size fits nicely under the cowl and with a pitts style muffler and an 11 x 6 Master Airscrew prop you have a perfect combination for the weght of this plane.

Out of my performance planes such as the Hangar 9 Extra 260, Twist and Funtana 40, I consider this the most fun in terms of zipping around the sky doing snap rolls and flat spins. It also lands nicely as long as you carry a little speed and even lands well in a dead stick as far as bi-planes go. The only negative is the color scheme as it really blends into sky and it becomes quite difficult to tell which side is up.