Im 6ft 3in tall, not overly weighty, and have not found a glider I couldn't fit in and fly comfortably. However, it's not pure height, but the dimensions of the parts of the body that may be important - I happen to be rather tall but evenly proportioned, so I 'passed' the RAF test for bang seats in all types, whereas shorter people with proportionately longer legs would not be able to fly in the Harrier, for example. Certainly, the K13, K21, Discus, Duo Discus, DG1000, Ash 25, Fox, various ASWs, T21, Pegase, and others, fitted me without a problem.
A more practical and pragmatic approach, at least to height, might be in order?