a) Orientation area scaling factor, κ_θϕρ, as a function of observer separation angle, θ, taken from its CDF (Figure B.4). The solid line is the relation at CDF = 0.5. This level is equally likely to be greater or lower than the true scaling factor, i.e. the one that recovers the true source area or volume. The dashed lines correspond to CDF  =  0.1667, 0.8333 and represent the central range that is twice as likely to include the true scaling factor. b) Area scaling factor, κ. Equivalent to panel a, multiplied by sin²θ. c) Fractional uncertainty range of the area scaling factor (dashed lines). The vertical dotted line represents the observer separation angle from the X-ray source of the SOL2021-05-07T18:43 M3.9 flare (95.4°), equivalent to 84.6° due to symmetry about 90°.