You simply can not expect to get away with doing this
Sounds like it will work but.... there will be issues!
The idea of using Photo Black on your Matte Black Cart or vice versa in order to circumvent the problems cause by a bad Black ink Switch valve ultimately do not really work.
Yes you can fool the printer but if you are using the Matte Black Cart filled with Photo black or the other way around, in order to avoid using a Black Channel that is cause problems with ink blobs, you will not be able to access the Paper choices you might want to access.
If you set the driver to MK and instead you've loaded your MK cart with PK, you will only be able to access MATTE paper choice. And vice versa!
You could simply just stick to one setting. Either PK or MK, whichever one does not cause any problems with ink leaks or globs.
OR.... you can replace the ink delivery system. There really is no other choice.
I am currently in the same boat with my R3000. I can only print with Matte. It does that flawlessly. Not so with PK!!

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