Masses of face-on distributions of spirals and discs on the y-axis, compared with corresponding spherical masses on the x-axis, from modelsTable 6, i.e. SEDs of spirals and discs that are similar to sphere-SEDs according to the limit , and their corresponding masses. The black dashed line is a common mass correction for the non-spherical geometries, C_M (combined) ≈ 0.03 ± 0.02, with the black dotted lines being the uncertainties. Mass corrections found with best fits to the EP Aqr observed data (see Sect. 6.4 for details) are included as a green cross (disc), red plus (100% spiral), cyan Y (5% spiral), and magenta inverted Y (0.5% spiral). A diagonal yellow line is included to show where C_M = 1.