I've finally processed the first part of the video I took sailing last Friday and then extracted the first 2 minutes so that I can post it here. The effect of the gimbal is quite clearly shown.
You can see that in this video, unlike the previous recent ones, the horizon stays level and the boat moves.
Yes that is a chimney, yes the heater was on, yes I do sail with the heater going (demonstrably) and yes, my deck and coachroof do need scrubbing!
More on that last comment another time.
As for the video, I thin the gimbal worked quite well except for one thing and that is having the camera plugged into the gimbal power port causes a lot of noise on the audio that swamps the sound from the microphone. I've removed the audio from this clip and I'll have to find a way to get rid of the unwanted noise for future videos.