Indeed, it is. I added the extra washer on the top of the bushing (I don't think it really needs one for function and the YouTube vid didn't use one IIRC), but it does stop the spanner from slipping down onto the headstock finish.
Only really clever people can see them.
But I'll hold off with final bridge on and fully strung pics until I can get some good ones. Today is turning out to be a day to leave things well alone.