QTR-Quadtone RIP

Setting out to generate new profiles for my 7500 recently re-inked
with black and three grey dilutions in KCMY; cm temporarily mothballed
with flush fluid. A straight ahead profile with a 50 ink limit has
blocked up shadows but linearized gives a nice greyscale, except that
there is a sharp shoulder at about 98% that leads to visible
posterization in one image with a deep near-black expanse.

I'm thinking of trying variable ink limits. The IL=100 calibration
suggests I should use K=35, C=70, M=80, Y=85 ink limits. Am I correct
in thinking I should print out calibrations with IL 35, 70, 80, 85,
then finding the percentage on the ink 1 IL=35 strip that matches the
100% patch of ink 2 IL=70; then the %age of ink 2 IL=70 that matches
100% of ink 3 IL=80, and so on?

I learned from Ron Reeder's pdf that black boost overrides
black/default ink limit, so I'll set black limit and boost at 35.