Solid line: an approximate representation of the derived f_ov as a function of stellar mass obtained by Claret & Torres (2019) while symbols: values of f_ov resulting from the comparison between the theoretical models and the observed absolute dimensions performed in the present study. The error bar displayed represents the typical uncertainties for unevolved or mildly evolved stars. For the more massive stars, beyond the calibration of f_ov by Claret & Torres (2019), we find an average of the best values from the same methodology to be around 0.025. The only slightly evolved massive system is V453 Cyg, which is discussed in Sect. 5.3, and shows a better fit of the observed parameters with f_ov = 0.03.