Hooray, got to the point where I've got APM set up and in a plane (Hawk Sky). Now I need a bit of help diagnosing a flight problem.
I took off and got some altitude, and then flipped into stabilize mode. As you can see from the video, as soon as I did this, the plane started spiraling down and to the right.
I brought the plane back in and recalibrated gyros, but still couldn't get it to work.
Any advice appreciated!
Update: As noted in the comments, I had the ailerons reversed.
Revised ground test and setup notes here.
Following that, here's what I did to reset and try again.