Variation of the projected radius at the maximum systemic radial velocity for 5 different values of its ellipticity (labeled in blue) with its major axis inclination. The observed projected radius at the maximum systemic radial velocity of FH Ser is marked by a solid vertical line, with 1-σ uncertainty marked by vertical dotted lines. In all panels, the black dot corresponds to the best fit value, with blue dots in the left and right panels representing acceptable values within the uncertainty of the observed parameters.