Famous classic boat designer, Ian Oughtred, got his start in the sporty Australian Gwen 12, a single trapeze, DIY plywood, double hander. He was class champion sometime in the 1960's. Andrew Chapman has been feeding me some Gwen 12 material including this article by Ian Oughtred on building the Gwen 12. This looks to be from Seacraft issue of boat plans.
The Gwen 12 was designed by Australian Charlie Cunningham in 1948 as one of the first stressed ply dinghies. Like most Australian designed plywood dinghies, the Gwen 12 was extremely popular in the 1950's, 60's, and 70's but died out in the 1980's. Below is the cover of the May 1958 Seacraft issue with what almost looks like a colored post card of the Gwen 12.
Here is the article by Ian in PDF format. Click here for 1971 plans for a double-bottom version of the Gwen 12.
Two restored Gwen 12's showed up at the South Gippsland Y.C. Australian Classic Wooden Dinghy Regatta in 2017.