Top panel: probability distribution of orbital periods and mass ratios of our synthetic population of semi-detached binaries. For the grey scale, see description in Fig. 7. Middle panel: as the top panel, but with the retrospect assumption of fully conservative mass transfer (see text). Bottom panel: evolution of orbital period versus mass ratio during the semi-detached phase of the 41 conservative Case A models of Wellstein et al. (2001), with primary masses of 12 M_⊙, 16 M_⊙ and 25 M_⊙ is marked by small purple stars. The small purple stars are placed with a time difference of 50 000 yr. In all three plots, the different coloured star symbols denote the position of the semi-detached systems in the LMC (Table 1), and squares denote the binary parameters of VFTS 450 and 652 derived by Howarth et al. (2015). The colour coding is as in Fig. 5. Red circles denote the parameters for the Galactic Algol systems.