I don't usually have a lot of sympathy for folks from Bermuda asking about sunshades but this summer here in Maine we have had a real summer, very little fog and plenty of clear days. So I too have been trying to stay out of the sun. (Alan I hope you understand a little Maine "Humour" (spelled for a Bermudian to understand) and a jab from your colleagues here in the cold white north of the US of A.)
Alan had asked to see some more images of the Aussie sunshade so I asked for and got some to post. This example is relatively short and there is nothing to stop you from going all the way to the transom with this design.
This is not a design as such. In Australia the metal working guys (a.k.a. the tinny) just come to the boat and create their own but they all look very much the same in style and function.