I asked Dazz, who started this thread and broke his foot, after the rather low trapeze-hook position.

I asked that because when sailing at sea and using the hookposition from the vid that is impossible. You are hit from the cat in the first wave you meet.

So, for me using a low hookposition, looks more something for flatwater sailing. Nevertheless I keep wondering why you want to chose for such a low position as is seen on the vid.
I mean he was hanging in an angle of more than 90 degrees to the hull.

Is that still usefull?? 90 degrees gives the most leverage, doesn't it. And even so, a footstrap is supposed to keep you from being pulled forward and not from pushed backward. So if there is a serious risk for that last, do not ever use the footstrap,