Included is a link below to a log from the latest flight of my quadplane. I appear to be having some sort of a yaw issue during the transition from Qhover to FBWA there is noticeable yaw movement which can been seen on the log as 4 decreasing peeks in ATT YAW. My question is how can this be stopped and should I also be concerned about the 4 large peeks when in horizontal flight .
Were you facing into the wind during the transition? Also, was the wind swirling at times? Do you have the weathervaning feature enabled? Did the transition to FBWA look ok in the air?
One of the differences between flying a copter and a quadplane is the large wing surface that can easily be moved by a breeze. Smaller, lighter planes can be pushed around until they start flying.
I would initially try another test with the Weathervaning disabled. If that reduces or eliminates your yaw issue then you can concentrate on changing the Q_WVANE_GAIN.
Sounds like a good test. Some other things to try is the link below and also consider the possibility of magnetic interference from the quad motors into the GPS/Compass module. Try using just one compass.