I sailed a Nacra 5.8 for many years and was sure that I could tell a 10 lb difference in the crew weight. While sailing downwind the boat just seemed to move a little slower in the puffs. In very competitive races that difference would add up as each downwind leg was sailed. Minor differences in weight really seemed to matter. However, for the past three years I have sailed an Inter-20. Based on my own experiences and those of others, I have yet to see anyone, including myself, sail a race where they could say that 10 lbs. cost them the race or even a place! The speeds are so great while sailing with the spinnaker that any little mistake is greatly magnified. The greatest gains and losses are due to poor spinnaker trim, slow raising or lowering of the spinnaker, or just a collapsed chute. While I do not understand why the light boats are not required to add weight to be class legal, and I do think that the class has made a tatical mistake in their weight deviation, I do not think that one sailor will lose a race sailing with a spinnaker because they are 10 lbs heavier.