Digital BW, The Print

I'm trying to use QTR's create-icc-rgb to linearize my workflow for
UT7 inks. I'm following Paul Roark's recipe for combining a linearization
with his Photoshop curves (http://www.paulroark.com/BW-Info/
Embedding_Photoshop_Curves_in_ICCs.pdf).

It seems to almost work. The problem is that the resulting ICC profile
is not at all linear at the high density end, and my shadows
get blocked up. I have tried both 21 step and 51 step targets, and
I have the same problem with each. I'm using a PrintFIX Pro spectrometer
and its measure tool to generate the input for create-icc.

Any idea what's going on? Has anyone seen this problem before?

--Daniel