I'm flying one with a Webra Speed .35. This engine is light and a real screamer. With a mousse can pipe, 5% fuel and an APC 9X7 prop, I have been radar clocked at 103 mph. AND, it is just simply a sweet flying plane. I never had any flutter problems, but be sure the elevator pushrod has no flex in it. At one time mine had a bit of flex in the pushrod and in a high speed dive it would take a LOT of pull on the stick to recover; not a good feeling. If you want speed, just remember keep it light! I have also flown them with a BB .25, which is fine for Sunday flying, but no real perfromance, as well as an FX 40 (too heavy) and an LA 40, which I thought was a pretty good choice, but just not the screamer that a good light wieght .32 to .35 will give you. This plane will do touch and gos all day, and when you take off and pull straight up out of sight, it's a pretty awesome feeling! The Enya SS will be OK, but as pointed out, a bit heavy.