Two practical time-optional controllers for rapid slewing of type-3 and type-2 third-order plants, PTOS3 and PTOS3tau, respectively, were previously proposed. In this paper, we present results showing that the PTOS3tau is more robust than the corresponding time-optimal controller to both plant parameter variations and flexible unmodeled dynamics. In addition, a useful numerical method to calculate the time-optimal controls for general linear systems is presented. The results for the PTOS3 and the time-optimal controller for type-3 third-order plants are similar and thus are not detailed.