I think the artwork is based on one of the 'dodgy designs' from Luftfahrt International No. 18 of Nov/Dez 1976. The magazine features a handful of drawings showing designs attributed to Messerschmitt, but which appear to have been inaccurately recreated from memory at a later date. The drawings posted by Justo are what the P 1106 really looked like. And there are further variations beyond those, but none of them look particularly like the Luftfahrt drawing.