I have been having problems trying the get a flatter curve on the throttle on my gas planes. Mechanically, when the servo arm to push-rod angle is 90 degree, the butterfly is half open. The verbiage below was taken off an article on the internet regarding 10X setup. The 50% statement is true for both of my gas planes. At half stick, I am making ~90% power. I have a JR 783 PCM radio and don’t have a curve mix or exponential capability for throttle channel.

What are my options? Digital Throttle servo selection? Alternative throttle linkage geometry?

“Yep.. you read right. Throttle setup is just as important to a smooth flight as anything else. I use the throttle curves (code 18) to make the throttle response as linear as possible. I want to hear an rpm change with every click on the stick. Most gas engines seem to deliver most of the power in the initial 50% of the carb movement.. so this requires a initially flat curve that then steepened sharply. It takes some playing to really get it perfect, but when done it makes it SO much easier to get a smooth, constant speed flight. Those of you without dedicated throttle curves can use a programmable point mixer and mix throttle to throttle to get the same effect.”

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

you could try an after market exponential mixer thingy that goes between the receiver and servo, they about ÂŁ12 over here.