We evaluate numerically the mobility of DNA chains under field-inversion gel electrophoresis (FIGE) conditions in the framework of the lakes-straits model introduced by Zimm (Phys. Rev. Lett. 1988, 61, 2965-2968; J. Phys. Chem. 1991, 94, 2197-2206). We extend the model by allowing both simple and also multiple-branched hernias; this is achieved by arranging the data structure used in the algorithm so that each fragment in a lake can be treated separately. We show that the existence of hernias allows the probe to migrate faster and that with hernias the mobility minimum in FIGE shifts to smaller field periods. These effects occur only if the electric field is strong enough. We also discuss the influence of the model's parameters on the mobility.