I always hold my APC propellers with a piece of cloth when loosening or tightening my prop nuts on my OS46FX and OS61FX. The prop edges are real sharp even after sanding ! I was wondering if it will be easier and more convenient if I were to lock my piston with a "piston stopper" (need to remove glow plug) and then proceed to loosen/tighten the nut without the need to hold the propeller. My concern is will the top of the piston get damaged by the stopper or the piston is sufficiently hard and strong to withstand the pressure. Tha last thing I want is a deformed piston !! Where can I buy a good piston stopper for my two engines? Thanks for the inputs ..........