If you want it so that at first, large movements in the joystick, result in small movements in flight controls, then extreme movements in the joystick result in extreme movement in the flight controls, do this.
Imagine a U shaped object with the very bottom being at the first one. Shape the sliders so it looks like the right half of the U.
So you can finetune small controls, but go to heavy controls if need be.
I myself, have the sliders set to a line.