Hi Lazy,
Sorry I did not follow this post yet. Sorry about your orientation issues. I can not test this at the moment.
I do not know what is in master at the moment. I always setup the XSens to North-East-Down = aerospace default.
What I always do is to select telemetry-mode calibrated in the GCS and check all signs of all gyro (roll right positive, pitch up positive, yaw right positive) and accelerometers (nose down: x=-9.81, right wing down: y=-9.81, bottom down: z=-9.81).
Then, in fixedwing mode all the euler angles are copied directly from the XSens. If pitch is reversed, put a minus in
struct FloatEulers att = {
-ins_phi+ins_roll_neutral,
ins_theta+ins_pitch_neutral,
-ins_psi
};
Putting a minus/plus/-180 will not affect the stability of the XSens nor the integrity of attitude computations as the XSens does not care.