I used to almost always get death spirals when I was activating RTH with FMA co-pilot. It's been a night and day difference since I added an FY-20A. The plane actually turns around for home without spiraling out of control, which means I can start fine-tuning all the numbers.
Here's a video of an RTH test with everything at default values, except turn prop gain, which was set at 43. It's the farthest out that I've activated RTH -- 2000 feet out.
As you can see from the video, initial turn is pretty slow and there's quite a bit of zigzagging as the test proceeds. To make the initial turn faster, I'm going to try changing the 43 back to 50. I'll also increase turn derivative gain a little bit at a time until I get rid of the zigzagging. I will also turn up all the gains on the FY-20A to about 50%; they were at about 25% for this test.