In the early days of RC sailplanes, light wing loading was the goal (such as 4 oz/sq ft) and we were even advised to fly with the trims, so as not to increase drag by control surface deflections. These were "floaters," which might stay up a relatively long time but wouldn't go anyplace in a 5 mph breeze. It was less of a go-find-lift to a sit-there-and-wait-for-a-thermal. That was dying out by 1980, and we began to realize that the same models, ballasted to 7-8 oz./sq. ft., would stay up almost as long in dead air but would actually move around the field in search mode. We started to build them stronger and heavier, able to tolerate zoom launches without folding, getting extra altitude which translated to extra air time. It takes about 1 oz/sq. ft. of wing loading to make a perceptible difference. With an adequate and accessible ballast compartment, it was easy to experiment--find the best compromise and best performance. I'm talking about gliders in the 100-120 inch size range, in particular.
John Agnew