Thanks for the clarification Ramrod, but since we are talking auto feather I took the assumption folks would read "Raisbeck mods" as referring to engine/props. My error. The Raisbeck mentions -52 engines and Quiet Turbofan Props, whereas ZCR had -42, so not applicable? Is it a prop thing, engine thing, or combination of both? And for what reason to make auto feather mandatory over and above the stock standard machine?