I can't remember the exact process, but I was able to compensate for it with DXTweak. My warthog throttles had the same problem, but after adjusting to min, max and middle values of the calibration, I was able to get them moving in perfect unison with just a teeny tiny amount of deadzone at either end.
https://forums.eagle.ru/showthread.php?p=3285693#post3285693