I just test run my new TH 75 and here is what I used:
Prop: Master Airscrew Scimitar 11x7
glow plug: the plug that comes with the engine, I don't know the brand.
fuel: Homebrew 80/20 castor oil 0% nitro
After about a tank I got a steady 14300- 14600 RPM without sagging and in the rich side with plenty of oil and smoke coming from the exhaust.
I hope this engine gets better with more run time.
So far I'm very impressed and very happy with it!!
Does anyone have readings with the same prop?