I have the APM 2.5 with compass on board mounted at yaw270 using Board Orientation (AHRS_ORIENTATION) but haven't touched the Compass orientation (COMPASS_ORIENT).
Should COMPASS_ORIENT also be orientated? or is this just for APM 2.6 when the board and compass can be facing different ways? This isn't clear in the wiki.
As yet I've only been flying stabilisation and FBW-A which I'm guessing don't worry about the compass and have read in the 2.73 thread of some people having trouble unless they disabled their compass.
Prefer to know the answer rather than work it out in the air :)