I've had my GRP all summer and still has steel pinch on the top. (3 1/2 gallons) The above post about Mugen drivers loosing pinch is funny to me because they decided to go with OS. I have an engine pinching business and the Model I see the most business from is OS. They lose pinch faster than any engine I've ever seen. I've owned a few of them as well. I love how they run. But I can't afford to resleeve the things every two gallons. The materials that the GRP engines are made of are simply second to none. Japenese engine makers aren't up to par with the Italians.