Problem statement: HUGE deadzone with Heli-X Sim on NG ACE-RC (possible on any other input device).
Solution is here, carefuly read all about calibration process, jstest-gtk-git works fine for me, as described.
Write your own udev rules (in my case, /dev/input/js* changes time to time):
Script (make your own, this is VERY important, do not forget #!/bin/sh ;), also this is not good idea to run udev script from user writeable file):
That’s all, folks, now your heli is very aggressive and impressive as expected 😉