It's been a while since I made a Z3200 print on Platine, but I do recall using the Canson canned preset as a starting point for ink limits and never changing the ink load from that point. I can say that in the case of the Epson 900 series, the ink limits embedded in the Premium Luster default setting seem quite right. It might be interesting to pull back the ink load as see what, if anything, you gain or loose.
Ernst knows a lot about the Z series. I bet he'll offer a suggestion.
John Caldwell