It's a generally accepted fact that the rpm curves on our engines, gas and glow are far from linear. What some do is use a point mix (JR) and set the rpm with a tach etc. Personally I've not had to do that with the 100 and 150cc engines I have. I do however set the travel to the maximums (JR 140%) and set the linkages on the servo and carb so that there is no further adjustment to that 140%.
In other words, do whatever it takes to make the throttle go from idle to wide open while using your largest servo resolution.
This for me usually gets a nice curve. I can hover, elevator, harrier etc. comfortably, as well as do precision flying with no problem.
Set the curve how you like it and go from there_bob