Indeed, gliders carry most of their load (for high speed high performance use) in the wing, not the fuselage. Of course the fuselage holds the crew (one or two pilots) and quite often an engine, however the water tanks for higher wing loading are inside the wings and can outweigh the crew weight considerably. Sadly the weight limit is set by regulatory and probably competition standards instead of technical possibilities, therefore it is much lower than possible nowadays, 850kg MTOW currently over here, possible are weights of well over a ton with wing spans of around 30 meters and aspect ratios around 40.