A 16x20 print is the same as my 40x50cm prints I had made from 35mm Velvia transparencies to Ilfochrome for years. I don't see how visible grain would put people off, but likewise, I also don't see what your concern is about the size of the enlargement. A TMAX P3200 print I had made in 1990 was enlarged to 20x24 to exaggerate grain in an image that features old world wrought iron, lace and a Ford Zephyr V. It was recently reprinted again.