Hubble diagram residuals for the highest-ranked flux ratios at maximum light. From top to bottom: prediction residuals using ℛ only; (ℛ,x₁); (ℛ^c,c); (ℛ^c,x₁,c); and using the standard SALT2 fit parameters (x₁,c). In each case we indicate the weighted rms of prediction Hubble residuals (gray highlighted region).