RE: What is the max prop RPM?
Way back when I had an Airtroncs Jet Fire 20. It was a modified Ugly Stick type of plane. I had an O.S. .21 SE car engine in it. I put a Macs tuned pipe and header on it. I was running 30% nitro and I was able to get an 8.5X6 to turn at just over 23,000RPM measured on my Ace tach. I was running Zinger wood props on it. When that engine got on the pipe, ooohhh man did it take off. It was my first more power then weight plane. It would roll about 5 feet and then straight doing rolls. Had great mid range and idled all day long. The power difference between idle and half throttle was not much. The engine only made tons of power wide open. It was not a good engine when it was out of the power band. It was finiky to tune too. It would eat glow plugs like candy. I ended up loosing it to a ripped of aileron. It was fun while it lasted.
Dru.