I would indeed flush before switching from one 3th party ink to another since not all additives are compatible.
Only with OEM it is supposed to be tested for unwanted reactions.
@Borut 's experience the octo magenta is OK after thorough flushing encourages me not to abandon these inks too soon, even if it is only for the (in my opinion very satisfactory) red.
I agree the PRO-10 is less easy than expected based on my knowledge of the 9500, but I did not buy this printer to have the same results.
Instead of accepting 80% of the result for 20% of the price of OEM I think 90% for 30% must be possible.
Since both Octoinkjet and Precision Colors suggest a cocktail, I could as well make my own .
My intention is not to mix different inks into one cartridge, only to choose a different manufacturer for some colors.
I am aware that there is a danger on the moment you change the cartridge, so when switching between 3th party inks I print a few full color pages to be sure.