Thank you Neil - that is greatly appreciated.
[EDIT-] Ok..grabbed a roll of portfolio rag and done a heap of testing tonight - with some interesting results.
I had thought I would find the settings for the 8300 would be the right ones for a 6350; but not so. Not even close.
Cant use 'Special 10' on the 63xx series as for some reason it screws up printing on A4 (no idea why; but I suspect it is something to do with the different way sheets are loaded into 63xx vs. 8300 printers). I tried it a few times in case I had screwed up a setting somewhere; but it just doesnt work with A4 sheets. Wasted a bit of paper trying this.
Best paper choice on a 63xx after trialling all the matt paper options is Premium Matt Paper (which is incidentally, same as Moab's Somerset Museum Rag custom media configuration file)
Head Height: Standard and Vaccume Strength: Strongest
Because the paper choice was different I decided to also run a test in ink levels and this differs as well. A setting of high is way way to much and has the ink almost pooling on the 63xx. Settings of Medium High and Standard show visible bleeding. Low, Medium Low and Canon Standard all look visibly identical (to my subjective eyes). Looking under a Schneider loupe the Canon standard setting appears the crispest (maybe - its really too close to call) - so I went with that. There is no apparent difference in depth of colour. Incidently.. these settings work out exactly the same as Moab Somerset Museum Rag; which makes a lot of sense since these are both 300gsm 100% cotton rag papers that even look almost identical. The Museo is a shade warmer and a touch smoother.
Anyway; hopefully this may help anyone else with Museo Portfolio Rag and a 63xx series printer. X Posted to the Canon Wiki.
Interesting that the settings are quite different from 8300 series printers.