It seems to me that teh Extra is pretty sensitive to thrust angles. I had one waher under the left and top sides of my emgine mount originally, and the plane flew well. The last time I had my engine off I added more down and right thrust to get closer to the specs in the manual. I added a thicker washer under the top and left sides. I really didn't like the way it flew like that. I have another engine change coming up, as I have secured the Canadian distribution rights for MVVS engines so I will be putting it back to where it was before. Big crate-o-engines showing up Tuesday!