Formula unit volume, V-m, has recently been identified as the key link to a number of thermodynamic functions and has given rise to an alternative approach to thermodynamics for modern inorganic materials (volume-based thermodynamics, VBT). In an earlier publication, we reported over 400 ion volumes for commonly encountered cations and anions derived from crystal structure data which can, in turn, be used to generate formula unit volumes for those ionic salts, for which crystal structure data, which is the preferred source of such volume data, is not available. The purpose of the present paper is to report a further 147 supplementary ion volumes. These are compared to ion volumes obtained from the summation of Hofmann's elemental volumes, a convenient and alternative approach for the estimation of Vm. It is shown that many elusive ion volumes can be estimated using these databases in tandem by adopting the newly proposed isomegethic rule and other volume additivity rules. Generation of volume data for new, hypothetical, and counterintuitive ions, as well as for traditional ions, is now a reality, as is demonstrated.