In order to maximize the transversal magneto-optic Kerr effect (T-MOKE) of a Au/Co/Au structure, we propose a method to obtain the optimum thickness values. A criteria based on preserving good plasmonic properties has been included as part of this method. Using the theoretical prediction, we grew Au/Co/Au trilayers and perform optical and MO characterization using the Kretschmann configuration. The results admit very easy interpretation in terms of the interaction between the magneto-optical and plasmonic properties dictating the optimal thicknesses of the structure. Moreover, we have grown and characterized the optimized structure finding good agreement with theory reaching, for a 532 nm green laser, a maximal surface magneto-optic (MO) signal enhancement of close to nine folds with respect to the signal without plasmonic excitation.