I believe ol' Hartley may still be in business. The sail dimensions may be available through his outfit. He has a book out on Ferro
, seems to know something about them and used to produce ferro boats, including the Tahitian. His construction ideas made sense as did his maintenance
It was awhile ago but try an internet
search and see what comes up. Don't expect too much info from the site. He was very cagey with the info as, of course, he wanted to sell his book.
By my reckoning if yours is a Hartley produced boat it was well made...one of the good ones.
Best of luck and happy sailing!