You misunderstood. If course it effects in general, but we calculated 3 different configurations and it turned out, that the two lighter configs only differ at landing speed. At cruise speed there was almost no visible difference. The config with the highest wing load was dismissed, as it failed the requirement for stall speed.Eh? A light wing loading doesn't affect cruise...? That's a new one! You should ring up all the glider manufacturers and tell them not to bother with ballast tanks and stuff. They'll be pleased to hear this news!