In studies on Marangoni type motion of particles the surface tension is often approximated as a linear function of temperature. For deformable particles in a constant-temperature gradient far from the reference point this approximation yields a negative surface tension, which is physically unrealistic. H. Zhou and R. H. Davis (J. Colloid Interface Sci. 181, 60 (1996)) presented calculations where the leading deformable drop moved into a region of negative surface tension. Here numerical studies detail the restriction of the migration of two deformable drops given in terms of the drift time.