The New York Yacht Club has been responsible for a number of level racing classes over the years. The most recent is the Swan 42 designed for the NYYC.
Anyone who has raced big boats around a closed course knows how dizzying it can be to try to calculate the seconds necessary to handicap the boats against one another. Even for the recent Transatlantic race the idea of rating a Baltic 46 against Rambler 100 or a Volvo 70 seems silly really. The boats are so different in speed they usually are sailing in different weather systems.
Apples and oranges. It happens in car racing too. Difficult at best.