The present work attempts to predict the mass spectra of structures containing many clusters of doubly charged ions as well as singly charged ions. The method is applied to dodecacarbonylo-triangulo-triosmium, Os(3)(CO)(12), a particularly difficult example for modeling. The starting spectrum (25 points) can be reconstructed satisfactorily with 2% precision into a full form containing more than 400 peaks, which is consistent with the experimental form.