QTR-Quadtone RIP

I just started using QTR with an Epson 2200. I downloaded and
installed the UCpk-IlfordSmoothPearl curves that Tom has so generously
provided. I made a test print using the Northlight Images standard
test file that I first converted in Photoshop to the QTR-Gray Photo
Paper space (using the icc file located in the QuadToneRip ICC
folder). I am  using the Photo black ink and a Windows XP machine.

QTR Settings: 80 cool 20 warm, ink adj 0, gamma adj 0
The print overall looks good except the deep shadows start losing
detail. Step 100 measures L 5.40, step 95 measures only L 6.34. From
step 90 and on, the L value measures much more separation between each
step and you can clearly see the steps.

What options are there for opening up the deep shadow between step 100
and step 95. The rest of the gray scale looks pretty good and the
tonality is close to what I see when viewing in Photoshop. I don't
want to adjust the ink level since solid black is nice and deep. I
don't want to use the gamma slider and open up the shadow at the
expense of the mid-tone.

Are there any other tools in QTR that could be used to make this
adjustment or modify the curve?

Thanks for your help.