I use negative expo (futaba) on all my models to give me a half throttle setting that gives me the speed I want from the plane at half throttle.

The amount of expo I use ranges from -30% on my Saito 72 to -100% on my OS 61 FX with tuned pipe.

Basically you are up against the law of dimishing returns.

While not the most accurate program in the world, Thrust HP gives the HP at 9.5k as 1.86, while 7k is 0.744. So about half throttle is giving a bit less than half hp.

Interesting isnt it