Actually I adjusted the servo trims so that all servo arms were perfectly horizontal. (Couldn’t get the trim values smaller, because of the mechanical restrictions of the servos and levers.) Then I adjusted the mechanical links to the swashplate so that it was level (or at least almost level, because I can’t do half or quarter turns on the ball links. Finally I corrected the trim values a tiny little bit to achieve a perfectly level swash plate. I used a swash leveling tool to be sure it’s perpendicular to the shaft.
What could also be important is that the swash is only moving about ¾ of the way of the stick. When the stick is near the endpoints the swash doesn’t move at all. But I guess that’s ok. I also redid the rc-calibration (over and over again), but this doesn’t help.
The PWM values Pixhawk is commanding in manual mode are:
Stick: left middle right
Servo1: 1290 1534 1744
Servo2: 1322 1580 1775
Especially on servo2 you can see it. From mid stick to full left there is a difference of 258 microseconds, but to full right it’s only a value of 195. Maybe you’re right and it doesn’t matter, but I’m always trying to do my whole setup very carefully, because I know it can help a lot to get the best out of the helicopter.