Well thanks for your replies, but 50% sensitivity didn't work out. I tried this out.
If I look in my system prefs the axis shows a correct calibration, the red bar being at the bottom at throttle pulled full back, 50% at 50% way and 100% bar at the end of the throttle way. Its fully linear. So my X-52 works correctly.
Anyway I have to cope with this for max one week, when my oe-xam Bell Pitch Lever will arrive and hopefully be compatible with this great game.