I ended up going the Vortex ROK Upgrade Route as my Rotax Cyl was not lettered and thus not elidigable. So far, pretty happy. Seems well engineered and performace is good. Seems it is becoming a more common engine at the repaved/upgraded OVRP Facility. $1,200 trade-in vs a Rotax Rebuild is a no-brainer. Only downside of the ROK is we have to run leaded racing fuel vs pump gas for the Rotax.