I was actually going to put Piezo Flush into the MK cartridge, and then just not use it. (Except to occasionally swap back and forth as maintenance, per your suggestion.) So PK would have #1 glossy, OR would have #1 matte, and MK would have flush (unused). I'm not looking to have "two different PKs"; I'm just looking to avoid ink swaps while still printing both matte and glossy papers.
Thank you for the "currently installed" black ink explanation – of course!
And great recommendation on "flushing" by printing the flush image. I'll edit it to only print from my new #1 matte (OR) channel by isolating that part of the image, and that way I won't use up any other ink while filling the OR line with this new ink in place of flush.
Once I do this, am I correct in assuming I would only change my matte-paper quads to swap the "K-curve" numbers with the "OR-curve" numbers? Since my printer has PK-black set as "currently installed" (which I would leave as such), I would leave the glossy-paper quads untouched, right?
You guys are great, with such wonderful support!