Effect of multi-moding, which increases the level of grating lobes at 857 GHz, making it close to the measured ones. Two stacked cuts are shown to enhance the visibility of the main grating lobes (top panel: cuts at ±26^°, bottom panel: cuts at multiples of 60^°). In blue is shown the single-moded RFFM plus constant dimpling fit at 353 GHz, and in red the equivalent multi-moded model, while the measurements on Jupiter are in black.