You might want to do some scaling. There's several ways to do it, every one is correct for someone. A linear scaling means that every move gives an equal response - does that make sense? I mean, if you tilt your stick 10% of its potential, the corresponding flying surface movement will be 10% of its potential. However, you can set the scaling in steps, meaning that in the middle a 10% movement will only have like a 5% effect. For continuity, either set the sliders in a linear pattern slanted from your desired middle action to the top in the right corner, or in an exponential curve if you so wish.