Residuals of the Tully–Fisher vs. mass-size (left) and of the Tully–Fisher vs. Fall relation (right). Data from SPARC are shown as grey circles, while the red curves are the 1- and 2-σ contours of the predicted galaxy distribution of the same model as in Fig. 1. The dashed line shows the slope of the correlation of the model. The histograms on top and on the right show the marginalised distributions of the respective residuals for the data (grey filled) and the model (red empty), respectively.