I like that one, CliveG.
I notice it is quite high up, presumably for headroom and light. Presumably in driving rain you could lower the topping lift and get more side protection, at the expense of headroom of course.
Our hatch cover has a removable garage section so in hot weather we can make quite a long opening in the cabin top.
We have made the cover long enough to cover this opening.
On a subsequent erection I slipped a boat hook into the open end of the boom and extended it out beyond the backstay supported by the topping lift that I moved to the end of the boat hook.
The cover was then fixed to the end of the boat hook.
This gave better cover to the cockpit in wet weather.
It looked a bit creased due to some sag between the boat hook and the boom.