I disagree. You have to remember that especially the older Rossi's are set up with high compression in order to operate on low nitro. Running them with higher nitro then 10% will increase combustion pressure and cause the engine to fire too early. running a hotter plug will make it even worse, running too large a prop will create even more heat and pre-ignition. In my earlier post I reccomended some specifics for prop size and glug heat range. Where do you think I got that information? I got it from using Rossi engines in my race planes for the past 3 seasons, I have gone through the learning curve with them and was fortunate enough to win a season championship with them this past season. Obviously I know what it takes to get them to perform correctly.