Most people who print 400CN on B&W paper crank up the filtration really high (grade 3.5 and above). I have printed it on RA-4 paper, and while the contrast is normal, getting the right colour balance is a b***. The orange mask in Kodak's film is designed for color paper. Ilford's XP2 does not have that mask, that's why it prints as a charm on B&W paper.