QTR-Quadtone RIP

I am having some difficulty setting up a new profile.

I print the ink limit page to characterise the inks. I then print the ink separation page with the limit slider set to where the ink saturates the page, in this case 85%. I look at the figures and measure and set the crossover points. I use the GUI to fill the figures into the curve creation page.
Then I print the 21 step wedge, that prints ok, but the densities at the 70%-100% end are all cramped up with very little difference between them. I use Photoshop and the step wedge script to read the 21 step values. I copy and paste these L* values into the linearization boxes in the GUI.
At this point the procedure fails with a message saying that the steps are not in order. They are in order but there is very little difference between the steps at the black end. I think the closeness of the steps is the problem.

Is there a method to reduce the densities at the black end. Highlight, shadow, gamma, etc so I can linearise the curve?

Cheers
Greg Nixon