RE: Patriot
Great looking plane! Enjoy it.
Ditto....... to Razor's post....
Thats a LOT of prop for an ST45. 10x9 is some serious load. If you bought a pre-tuned system from MACS, it is tuned for 14.5k rpm or higher. Likely set about 12" for around 15-16K rpm. You want to prop it to get up there.
IF you are turning a 10x9 at 13.8K, thats not a bad engine!
Put a 9x7 or 10x6 APC on it, see if it gets up into the 15K RPM range. Let it unload.