Which Canson Rag are you using? Sounds like you like it.
I switched from Hahnemühle Photo Rag 308 to Canson Rag Photographique 310, for the reasons outlined above. It is about $20 more expensive than the Hahnemühle in 24 x 36 inch sheets, but that isn't always that way. The Hahnemühle smooth rag is a little smoother than the Canson rag, the regular Hahnemühle rag is the next smoothist after the Canson rag, and Canson BFK Rives has a slight surface texture, but not as much as a St. Cuthbert's Mill Velvet paper (Epson Velvet Fine Art, Epson Somerset Velvet, Moab Enhanced Velvet, Canon Velvet Fine Art, Breathing Color Elegance Velvet Platinum, etc).
I hope my mk cartridge will still fire up.
That has never been a problem for me. It is one of the annoyances of the 3880: accidently choose a printer with the wrong paper type (mat vs photo), and it will go ahead and change inks without any warning or question. Even if you turn it off or cancel the print job, it will continue to change inks once you turn it back on. A warning dialog would be nice, like: about to change from mk to pk, do you want to continue: yes or no? The 7890, 7990, 9890, and 9900 all manage to ask first.