I think I throttled all the way from standing to top speed to start. What I noticed was that once at top speed (33 mph on the meter along level roadway)if I rotated back about 20 to 30 degrees there was no noticed difference in speed or engine sound. Farther back than that, and the speed would start to drop. Going up a grade I throttled all the way to get the most power and speed, but even there I'm not sure that I had to......I guess it will take more time to get a better answer.
Oops...I should not have used % in my question.