Since the seminal work of Liljencrants and Lindblom (1972), a key testing ground for functional, evolutionary, or emergentist approaches to sound systems has been the typology of vowel inventories (for example, Lindblom 1986, Schwartz et al. 1997a, de Boer 2000). An important innovation of Schwartz et al.'s Dispersion-Focalization Theory (DFT) was calculating the optimality ("energy") of a vowel system as a weighted combination of two separate auditory parameters: (i) dispersion: maximization of the auditory distance between vowels (as in Liljencrants and Lindblom 1972), and (ii) focalization: maximization of the importance of "focal" vowels such as [i] and [y]. We report results of new vowel system simulations following the original DFT formulas of Schwartz et al. However, our means of selecting candidate systems for comparison explores the search space more effectively, allowing for more thorough and accurate computation of DFT's predictions. In particular, we find a greater number of optimal systems than originally reported for DFT by Schwartz et al., many of which have analogues in the UCLA Phonological Segment Inventory Database (UPSID; Maddieson 1984, Maddieson and Precoda 1989).