Mass-radius evolution (solid line) of detailed accretor models for different initial periods (colour) and initial accretor masses (top 4 M_⊙, middle 6 M_⊙, bottom 8 M_⊙). The donor always has an initial mass of 10 M_⊙. The size of the accretor Roche lobe and L₂ sphere are shown as dashed and dotted lines. We used crosses to indicate the maximum of the mass-radius curve (R_max, M_R = Rmax) according to Eqs. (7) and (8), based on the maximum mass-transfer rate of the detailed model. The plusses indicate the same, but for an estimate of the mass-transfer rate based on the conditions just before the RLO (Eq. (9)). When a symbol is placed at a high radius but at the initial mass of the model, the model is expected to swell unstably, and the radius is the Hayashi radius (see Sect. 3.1).