What they're suggesting is that the normal 80mm lens is not formulated/corrected for close-up work. Thus, as the magnification increases with longer extensions, the image quality falls off. The trick of reversing the lens, often used on 35mm SLRs, doesn't work with Hasselblad lenses because of the shutter linkage, of course. For maximum image quality, you should stay within the design parameters of the lens, or switch to one that is designed for macro work, such as the Makro Planar. But, if the 80mm lens is what you have, try it, and judge the results by your own standards.