Just as a note... The one thing that I noticed from talking to end-users about clogging issues specific to yellow (in CLI-42, CLI-551/251Y and others of the same later generations) is that it wasn't hard for people to contaminate their equipment with water. So, regardless of any ink formulations that don't trigger the jelling reaction themselves, there's always that lingering potential that something else might, if any of the OEM ink remains.
Granted it would be preferable to avoid any need to flush out original inks, but the added benefit of flushing is that it cleans out the OEM ink and leaves everything fresh for your new refill ink so you can get on with profiling pretty darned quick rather than waiting for the old ink to dilute down to nothing.
