The nacra 20 sailplan could probably gain a little from some development - but the reason F18's pass an I20 when the wind is up (and it's on the nose) isn't because the sails. It's because the N20 has soo much horsepower and gets overpowered so soon. When I'm sailing a N20 upwind with the wind at about 12 to 14 the downhaul is maxed out and the top of the sail is doing very little to propel the boat but is still adding drag. We don't max out downhaul on the F18 until 18-20 knots of breeze so the F18 in 15 and above has a signifiantly more efficient sail area. It's less about efficient sail plans than it is about a reduction in horsepwer....if you could effectively reef an N20 main you would probably have something (but your sailshape goes to poop).