This paper presents a new method used to determine the optimum group configuration of any specified number of piezoelectric actuators for vibration control of a flexible aircraft fin. A finite element model of the fin was used to obtain the frequency response function (FRF). The fitness function for optimization using a genetic algorithm was derived directly from this FRF, eliminating the need for a closed-form analytical solution. In comparison to the existing approaches, the novelty of this method is in that it allows optimization on much more complex geometries where the derivation of an analytical fitness (cost) function is prohibitive or impossible. Optimum configurations of pre-determined numbers of actuators are presented for single mode and multi-modal acceleration and displacement control criteria. Group efficiency and control authority are also examined, allowing a suitable number of actuators to be selected for any application. Actuator efficiency was higher for single mode control; however, actuation authority was much higher in multi modal control, reflecting the fact that it is desirable to select actuators that are able to exert substantial control authority over several modes.