In heavy air you need to use a #3 so the boat will point and isn't overpowered. In light air I had a 1/2 Oz spinnaker that was class size and legal for PHRF (not One Design). It made a big difference for winds less than 7 kts. When I had Rhapsody, I raced against a well sailed S2 9.1 and we mixed up the results regularly with these sail combinations. The results were based on who sailed the better race because from a boat speed perspective, the two boats were pretty well matched.