Back in the days of stock plain bearing engines in Profile Carrier the trick was to put the G21 piston, sleeve and head into a plain bearing ST 35RC, thereby making into a CRC. World Engines had announced that the CRC as coming, be we didn't have time to wait.
That left me with a low milage Stunt piston, sleeve and head which went into a G2 case and served as a stunt engine. The Stunt pistione' y cylindre' was a clear step down in power from the combat setup.