Digital BW, The Print

I've been printing with VM-Inks and Paul's mw curves,with good results. Just
that
in the shadows,I've been having posterization. When I print a 21 step
wegde,90,95 and 100% look very much the same,the rest of it is ok.
I've tried the Jerry Nevins aproach Paul suggested on the list,tweeking the
dot curve for grayscale space to separate them,but results were not good.
Would it be better to try to tweek Paul's mw curve in any way? In what way?
I'm
a bit frustrated here... Monitor is calibrated,so I'm satisfied with
gamma correspondence,it\ufffds just this posterization problem on shadows
that bothers me...
Best regards,
Andr\ufffd Vallejo
Brazil