I have a Weston Magnum with hundreds of flights on it. I run a OS 46 AX and a Mac 8.5cc tuned pipe. I run the APC 8x9, 9X8, 9X9, 8.75X9.0W PYLON. 30 % nitro. With the 8X9 I can get over 18,000 RPM static. Of course it really unloads in the air at least another 3-5 K. (Especially in full throttle dives!) This motor pipe setup is so reliable I never really have to touch the needle or worry about a flame out. It takes about a minute for this motor to warm up and then it runs exactly like an electric motor. The only thing this motor occasionally needs is new glowplug. UNLIMITED VERTICAL and great top speed. The photo is old, my header and pipe are both shortened to the max now.

EDIT;
Actually, I flew it yesterday and threw the tach on to see what it was turning for the purpose of this thread. I saw just over 19,000 rpm for a moment with a 9X8 APC. Didnt touch the needle.