Calix[4]arenes are excellent ligand supports for the synthesis of polymetallic clusters of transition and lanthanide metal ions, as well as 3d-4f ion mixtures. Bis-calix[4]arene, a recent addition to the calixarene family, forms structurally related cages that mirror the metal ion binding preferences of calix[4]arene. Here we show that stoichiometric control causes remarkable expansion in the cores of two known bis-calix[4]arene-supported clusters, with concomitant changes to the magnetic properties observed.