Ratios of extents measured from the (u,v)-plane and from the abundance profiles. The lower axis show the measured ratios and the upper axis the corresponding luminosity ratio calculated using Eq. (4). R_{CO,no history} has been calculated using a wider (u,v)-coverage spanning from 5 kλ to 200 kλ, to get a good reference value. R_CO,history has been calculated using the standard (u,v)-coverage.