The issue is that the weight on the gimbals doesn’t count toward your copter’s rotational moment of inertia. So, when you fly with a “dummy weight,” you’re not getting the right gains. Maybe if autotune will run with a dummy weight on the gimbal, you should try that? Otherwise you should back your gains way off or manually tune with the gimbal on.
I finally got the copter back in the air today. I did an auto tune without the gimbal and as you said the results were much different with lower gains. The copter felt a bit loose so I increased them just a bit which seemed to improve things.
It was flying well so I went ahead and added the dummy weight to it for further testing. So far so good. Tomorrow I’ll do some flying with the camera/gimbal if the weather is good.
Thanks for your help. I’ve learned quite a bit which is always good.