Heliospheric evolution of the flux rope radial size S[AU] versus distance R[AU] for runs A2-A6. Only the range a>2 (R>0.29 AU) is considered, to avoid the first dynamical transient for most runs (even though it is still visible and important in runs A4-A6). The estimates of S using σ_x are drawn as markers (different shapes for different runs), and each run has been fitted with a power law (solid lines with different colours). The solid thin black line is the linear (α_R≡1) trend. The shaded grey area highlights the range between the minimum and maximum α_R values obtained by randomly sampling data points from the combined set of runs A2-A6 (see text for details).