With Ardupirates and earlier versions of Arducopter I had a problem with gyro drift. I thought this was not a problem with the 2.0.46 version I'm running now, but I have started to notice it again when flying in windy conditions.
With Ardupirates code my quad had lots of thrust available to carry camera. It was unstable if giving full thrust, so I had to turn down the thrust to about 75% by adjusting throttle Endpoint(EPA) on my transmitter.
The quad flies ok in stable mode when I trim the sticks, it hovers perfectly for a while. But after short time, the center of the sticks is not neutral anymore. After a while, max stick input is almost not enough to keep the quad straigh