Single-manufacturer one-designs (SMOD) are very much in the minority as far as one-design classes. What is there besides the Vanguard classes and the Hobie classes? (I don't know what the deal is with the sailboard classes.)

The Optimist Dinghy Class is the largest in the world right now, and they have a huge list of builders and sailmakers --and plans available for building the boat yourself.

When we got our Lightning in 1948 it was the largest one-design class in the world. It had a number of builders, and you could get your sails anywhere you wished (as long as they measured in).

The Tornado also can have many builders and sailmakers, and you can also build it yourself, but all have to comply with the measurements and tolerances.

Those are examples of TRUE one-design. SMOD's are not true one-design, because they force the crew to be one-design, too.