I have sold my '65 M20C.  While searching for its replacement M20J,  I have come across a few Rocket Engineering conversions.  I am interested in your knowlege and opinions of the upgrade, The upside is clearly advertised, what are the "hidden" downsides. Background according to Rocket Engineering:  "The 300 hp, normally aspirated, Continental IO-550-A engine provides out of this world performance for the Rocket Engineering 300 Missile conversion."  "Hartzell 3-bladed, full feathering propelle