2/3rds stopped down works fine for enlarging.
If you are doing alt processes with contact printing -- you can go all the way to f64, f128 or f256 (or more) with no effects....the edge diffraction effects just don't show with contact printing.

So if you have an 1100 XXL or 1100 Doktor Geronar or 42 inch Artar or other long lens with almost no depth of focus wide open, you can gain extra depth of focus when you need it. (again faced with slower exposure and more reciprocity effects).