Virtually all the open regattas that I have attended give 5 or more boats of the same class separate scoring. So then if you would rather race open or class (one design or formula) becomes a non issue. I have never heard any of the sailors that made up a class complain about racing against each other rather than being a part of the open fleet. For my outlook, if there is one boat in my class that is who I race against and the finish within the open fleet is not that important. Open racing does give you a lot more time on the water that wouldn't happen if you just do class racing.