Here's a low res image of the sail plan, which might help.
The sail area is 16.7 sq m.
Information taken from NZ Trailer Yacht Association website
https://www.nztya.nz/designs-d-j.html
the page is a bit untidy, -- select "Hartley Pg 3"
or click here
I am away from home at present but can get some better images later if you want.
This used to be an iconic NZ design, most of them home built, but few people build anything these days and you don't see so many around now. It was one of the first trailer yachts around, and I think it was this design of Richard Hartley's which gave us the term "trailer sailer".
Good luck with it.