It looks like you are using SERVO11 for Left Motor Tilt (75) and SERVO12 for Right Motor Tilt (76). Each SERVO output has these settings:
You can change the til from up to down by changing the flight mode from QSTABILIZE to FBWA. This can be done via the R/C transmitter or from the Mission Planner Actions tab and MODE button.
If the servo goes in the wrong direction, change REVERSED from 0 to 1 or from 1 to 0. Does this makes sense?