So from main screen go to options>controls>axes and click on the elevator tab. You should see 5 bars appear at the bottom of the screen. The right hand 2 show the sticks INput into computer and the OUTput into the game.
move elevator and watch the bars move. If all 3 of the left hand bars are set to 0.00 the in and the out bars should follow each other smoothly and exactly.

Of the left hand bars;
Sensitivity controls sensitivity, fully left the output should mirror the input (same as 100's across the board in old IL2 terms). Moving it to the right makes the stick less sensitive in the middle but should still reach maximum deflection.It applies an 'S' curve to the input in proportion to how far you move the slider. Change to suit what you think is realistic works best for you, but would recommend starting at 0.00
0% Dead zone controls the deadzone at the axis centre, left is no deadzone and 1.00 is the maximum deadzone. A deadzone is an area in which stick movement will produce no output into the game, as you don't want this behaviour I recommend 0.00.
100% Dead zone controls the deadzone at the extremities of movement in a similar way to 0% deadzone.

IMPORTANT- when you have the settings to your liking. based on the in/out bars, click the APPLY button, if you hit back any changes you made will not be saved.