Digital BW, The Print

Hello,

I have an Epson 4000 which has 8 different inksets. Two of them are for
blacks, one  for matte paper and one for glossy paper, this means the
printer is using only 7 inks for a print.

Is there a possibility with a Rip (QTR?) to use the 8 inksets, using one
of these two black for some other ink like gray for example.

Thanks

Michel