1σ confidence contours for cosmological nuisance parameters, as in Fig. 15, now for forecasts employing the comb + shift model 𝒩_comb + δz_i for internal redshift calibration (Sect. 2.3). The comb + shift recalibration reduces biases on the S₈ − Ω_m plane with respect to the ‘do nothing’ (Fig. 13) and shift (Fig. 15) models, and recovers some of the FoM lost to the shift model even whilst marginalizing over scalar shifts.