Hertzsprung-Russell diagram showing the two stellar evolution tracks calculated by Marchant et al. (2016) that are used in this paper. Only the evolution path of the primary is shown, since the evolution of the secondary is virtually identical after the initial mass transfer. The blue filled asterisks mark the positions at which stellar atmosphere models where calculated. The labels near these asterisks are the atmosphere-model identifiers used throughout the text and Tables 1 and A.2. The highlighted and color-coded parts of the tracks refer to different WR phases and the period where the Roche lobe volume is filled, respectively (see inlet).