To be right you would need to take a head shim out and run a hotter plug in the motor.
I run 15% nitro and now run just 0.1mm head shim and a No:5 plug.
Re-tune the carb and away you go.
15% nitro, 18% oil and at $11 a gallon. I like it. Especially if you really don't need the utmost of power. I run this in my off-road car and for bashing around.
So enjoying building cars I sometimes forget to save some "man-time" to race them!?