How much does your bipe weigh? You don't need more rpms on these motors because they swing props with lots of pitch to compensate. From what I hear, you should definately stick with the recommendations for prop, fuel, etc. If other 120 size 4-S would be enough, this one should too.

I hope you meant 20cc since this would translate to 1.20 size.

Have you thought of mounting a conventional 120 inverted?

Marcus