Answering my own questions - partly.
I was not able to make the diode wire hack in the instructions work for the rack case. I can see that it would work for the console case: but the rack case has a small lip that comes further in towards the PCB than does the console case. The
upshot is that I wasn't able get a soldering iron down on the possible
solder points without damaging either the PCB and/or the acrylic
lip.
As has been kindly pointed out to me privately, the Otto panel has a nice little pad in its upper right corner (seen from the back) that is designed for soldering in a (diode) wire that then runs straight into a perfect little hole on the PCB that would make this prefabricated version of the hack a dream to solder up. Alas, and perhaps understandably enough, the little pad is not included on the two regular front panels. I did try to use it with a (diode) wire soldered to one set of the connecting solder pads running along the top of the case: but the resulting angle between the anchor on the top of the case and the little hole in the PCB made it impossible - for me, at least - to force down the PCB far enough before the solder solidified. An additional hand - or perhaps a C-clamp - to do the pushing while two hands control the soldering iron and solder application to the wire/hole might have worked a bit better: but I had neither of those available.
I did manage a good improvement by way of a simple, short, notched wooden dowel wedged between the PCB and the lip of the rack case. But the middle top row of lights remain partially swallowed up by the front panel that still bows out slightly. While there are certainly worse problems to have - the Otto panel worked perfectly with the console case, such that all the lights came through with exquisite uniformity. To paraphrase the instructions: the contrast is annoying, but at least less so now than a few days ago.
Simply as a suggestion for improving the instructions and documentation for future builders. Yes, if you have the rack version with two front panels, you can use one of the front panels as an ersatz Otto panel for the second case. But also yes: you should follow the advice to build the rack case first if at all possible. While not further explained there, you can apply the diode-wire hack to the console case build when using the second front panel as an ersatz Otto panel, should the hack be needed. Not so, at least so far as I was able, to the rack case.
I hope this doesn't come across as somehow snarky, overly obsessive-compulsive, nit-picky, etc. I am 99.99% ecstatic with the completed build - and only hope that a note like this will be helpful for future builders and/or enhancing the documentation. A thousand thanks again to Oscar, Jose, and all the other hands and minds that made this wonderful kit possible and available.