Fred and VB,
The original post didn't specify 2C or 4C. "I have five flights on the 120 now. Here is my set-up: GP Venus II with O.S. 120."
Being a 2C flier, I assumed 2C and my comments were for the OS 120 AX.
If this is a 4C we're talking about, then my comments about nitro content don't apply.
I agree that 15% is a good choice for the 4C OS.
Regards
JC