I think there must be a misunderstanding here. A spi will get you much, much, faster around a windward/leeward course, at a penalty hit in the area of 2% upwind. If you are going to do tight reaches, a overlapping jib (or selftacking jib) might be better, but once you get to a broad reach, a similar boat with a spi will leve the non-spi boat behind like it was anchored.