Single crystals of the 1,6-hexanediol Dianin's clathrate have been studied by Brillouin spectroscopy to obtain its complete elastic tensor. A reevaluation of the elastic constants of the structurally related heptanol Dianin's clathrate is also presented. These results are used to elucidate the microscopic origins of elastic trends within Dianin's system on the basis of guest size, shape, and functionality. The guests cause a reduction in stiffness compared to the clathrand. Decreased stiffness of the c(33) elastic constant with expansion of cage hydrogen-bonded hexamer rings at the top and bottom of the cages is associated with competitive guest hydrogen bonding. The bulk moduli and linear compressibilities calculated from the elastic tensors are presented and acoustic absorption results are shown to be consistent with thermal conductivity measurements.