Thats completely correct Mary. If there was a "fleet" of 8 Hobie 16's (or 18's or 14's for that matter) starting in an overall fleet of 80 boats of various size and performances, the Hobies would race equally with all the other "classes" with their regatta results calculated using the "back calculated" handicap system together with everyone else, thereby featuring in the overal positions, BUT as they were of OD they could also have their own class race within the regatta as their class result would be "over the line first".
At this club many classes of cats conducted their state heats there during the course of the clubs normal racing just so they could get their state championship results and still compete in a mixed regatta as well, so of like two for the price of one.