I think that last video confirms that it works OK. You cannot blame the equipment for the lack of operator skills.
I would not be surprised if that gimbal and S800 motor combination didn't work as well or even better on the smaller 550 frame with better motors.
The best airframe stability that I have ever seen on anything is the latest F1-535 Ultra light for gopro size cameras, it weighs 1.6 kilos complete plus battery and camera. Almost the same weight as the Zenmuse gimbal. Check out the size of this camera mount. It is sub .005 degrees. In other words at least as accurate as the Zenmuse.
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Rock steady video is old hat these days. It's all about how small and light you can make it to go with the new camera technology that is coming.
Hauling male jewelry about the sky is just getting too dangerous I feel. Legislation is coming. Weight limit, rotor protection. line of sight operation etc.