Sorry for not responding sooner, I have been out for the past several days with a stomach bug, so am finally back in the office and catching up on emails.
The 9890 printer has a total of 9 cartridges, but only 8 print channels (only one black prints at a time), so if your C and LC channels aren't printing well, you're left with 6 useable channels, which is just enough for a custom K6 matte setup (as long as all other channels are working well).
With a bad C and LC channel, I would like you to set up the Piezography ink shades in the following order:
MK= Neutral shade #1
PK= PiezoFlush (unused)
C= PiezoFlush (unused)
LC= PiezoFlush (unused)
M= shade #4
LM= shade #5
LK= shade #6
Y= shade #2
LLK= shade #3
With Piezography ink shades in the above order, I can make you up to five curves modified from existing curves for your shade placement, or two custom curves for your specific printer and ink setup. The cost of either five modified curves or two custom curves is $100.
Please let me know if you have questions or there's anything else I can help you with.