Resulting values for γ (colour) and β (lines in lowest graph) for the initial parameter space of WR9. Each integer value of γ is marked with a solid line. The shaded boxes indicate whether mass transfer will be stable. Parts without shading will be stable, lightly shaded parts can be either stable or unstable, depending on the exact value of q_crit The heaviest shaded parts will always experience unstable mass transfer. The dashed line indicates the period boundary for Case B. Dark grey shades indicate excluded mass ranges (see text).