I had a bad "drumming" problem as you put it, with a Saito .72. I didn't think much of it. Then after a small mishap, I decided to re-cover the plane. This was the first weekend I have flown it since the re-cover, I thought something was wrong with the engine because it ran SOOO much quieter. All of the drumming went away. I think it is a result of the covering not being tight, or not as tight as if you had done it yourself. Sounds awesome now!