QTR-Quadtone RIP

I am very new at this. I'm looking for help . I have
been
exploring QTR with UT7 inks on the 2200. There were two profiles provided in the
QTR
download for matte paper.
1)UT7-EEM_cool
2)UT7_EEM_warm
I printed out some 29 step grayscales {standard 21 step with additional steps at
either end
to closely evaluate shadow and highlight regions). I printed these with various
blends of
cool and warm. They uniformly exhibited what appeared visually to be very good
tonal
separation. However there was one problem. In the 96% to 100% region there was
severe
banding as well as a lightening of the tone. Nozzle and alignment checks were
performed
prior to printing the grey scales.
I printed the greyscales useing Roark's Curves and this problem did not occur. I
would
really like to continue with QTR. Has anyone encountered similar problems when using 
these profiles? Does anyone have suggestions as to resolving
this
difficulty? Any help will be very much appreciated.

Howard