Six reference pixel designs for an assumed planet position (cyan asterisk) in the upper dark hole of a gvAPP180 PSF, as shown by the white pixels. Upper dark: choosing reference pixels from the dark side of the same PSF; upper bright: choosing reference pixels from the bright side of the same PSF; lower dark: choosing reference pixels from the dark side of the complementary PSF; lower bright: choosing reference pixels from the bright side of the complementary PSF; upper dark+bright: choosing reference pixels from the dark and bright sides of the same PSF; joined dark holes: choosing reference pixels from the joined dark holes.