...to really understand it I think requires a high level of very specialized education and experience...
....I'd be surprised if the rest of us will be particularly reliable at second-guessing them...
Don't worry I'm not fragile.
Listen I'm just a lowly 47yr old college drop-out carpenter who loves photography and (still) races motorcycles. You're not gonna learn much from me here and I'll be the first one to tell you that. But do keep in mind the genius buddy who I continually make reference to - he actually has a very specialized education which applies to more than just one aspect of these piezoelectric printheads. While I respectfully appreciate that you might expect a "genius" reference from a carpenter's perspective to simply mean "Wow that guy's smart," what I actually mean is - he's a genius. Keep in mind where I live. I used to wave to Steve Jobbs on my way to work in the morning, he literally lived up my street. The flip-phone was born above the very wood floors I'm writing this from. This area that I live in right now, which I don't even understand how I live here, is a mecca for the mindful. And our resident genius - who has access to more people just like him - has earned his his seat among the best of them. It's a safe bet you hold in your hands today, Mark, something our very genius made yesterday. Literally
I feel incredibly fortunate to have the very specialized help we do here. There's not as much "guess work" going on as my goofy nature conveys. Would you like me to explain exactly how just forty six microscopic brass leads inside a channel's tiny ribbon wire can deliver firing charges to seven hundred and twenty individual Piezoelectric nozzles - all needing different information? Because I can do that - all the notes are scribbled on three napkins from Thursday night's dinner at California Pizza Kitchen. That's the type of specialized education we are fortunate enough to have access to here. I have to brace myself before I ask questions. Seriously some of the answers I get leave me feeling pretty dam helpless. It's common I'm lost at the first sentence, never mind the last.
As for "that lingering issue is...well, still lingering :-)," consider this fun fact and then tell me YOUR answer: The 9900 that I bought in Colorado had a reported 75% of it's green channel missing. I bought that printer in August, where it was dragged from the back of a mini-van packed with four hundred suit cases and bicycles and juggling apparatus's piled on top of it. For a week it baked in the back of my cargo van in the high (dry) desert heat (110+). Once I got it home that machine lay inactive, never even turned on, for 4 months more. So it's been abused - subject to horrid neglect, super high temperatures, super dry environments, banging, smashing, vibrating and the like. You name it this 9900 has endured it. For sure way more than my shipped 7900 ever endured. The 7900 was back up and running in only ten days time from the day it was shipped, which was also the day it reportedly fired it's last print - and it had terminal clogs from (my) day one. So what would you expect a nozzle pattern to deliver on this 9900, after all this time and abuse? Maybe not one channel firing one nozzle at all? Well you'd almost be right, only magenta was 100% clear. The rest of the channels/nozzles were pretty much gone. After just one series of pairs cleanings (about three per pair), this 9900 was 100% clear and ready for printing - except for the very same 75% of missing terminally clogged green nozzles that we missing before I got it.
I don't know what this does for you, but it pretty well wraps up my view of the 7900 that I bought used.