Walker will probably give a more technical answer to your question, but here is a practical one.
The purpose of Ink Limiting is to take care of the heavy lifting of getting the .quad within the bounds of the printing process <span style=“text-decoration: underline;”>before</span> beginning the process of linearization. Since you are printing palladium with a small amount of platinum, the existing limited master curve that installs with PiezoDN is already ideal for your printing process. But what if you were printing cyanotype which has a much shorter tonal scale? If you print the 129-step target with the Master curve and find that 2 or more highlight steps (beginning with step 1) are pure white, then in order to get tone in those steps you need to adjust the ink limit on that end of the curve. PiezoDN is designed so that the maximum at step 1 remains constant, but from step 2 on down it should be adjusted for the process.
As another example, I have just this week set up a 3880 with the K7 Carbon inkset rather than the Selenium which is standard for PiezoDN. The Carbon inkset have a higher UV density than does the Selenium, so I found it necessary to adjust the Master curve to suit the inkset. It was not a large adjustment, I think I could have gone a little further, but it brought the highlight tones down enough that they could be linearized easily. BTW, I am profiling for pure palladium.
I’d also like to comment on the phenomenon of solarization that you mentioned. It is indeed something that is more likely to occur when printing pure palladium, but it is also a definitive indicator of overexposure. If you get solarization regularly, it means that you have exceeded the optimum exposure time for the materials that you are printing and the conditions in which you are printing. By conditions I mean the environmental conditions in your workspace as well as certain procedural things that may be part of your “workflow”. Temperature and humidity come into play, how you dry your coated paper, whether you rehumidify before exposure, and if so is it in a controlled way, are very relevant to whether or not solarization may happen. The relative humidity in my darkroom stays between 50-65%, but temperature can vary seasonally from 60s in the winter to 80s in the summer. I have found solarization to be much more likely at higher temperatures, and that is when I have to pay extra close attention to the drying regimen. I long ago abandoned the use of forced air to speed the drying process (except with certain Japanese papers, but that is another story) in favor of simply allowing the paper to dry until no longer damp to the touch but still slightly cool. This is generally between 5 and 10 minutes, maybe 15 on a large print.
I recently made a series of 21-step Stouffer step tablet prints of a new paper, as is my long standing practice, to characterize it’s tonal scale and contrast response. A couple of the test prints showed slight solarization between steps 1 and 2. I knew that I had been distracted and that some had dried for longer than others before exposure, so I did another test it which drying time between coating and exposure was the only variable. I used 5, 10, 20 and 30 minutes. The 5 and 10 minute intervals had Dmax readings of 1.42, but the 20 minute test fell to 1.28 and the 30 minute to 1.26 at step 1. Step 2 was slightly darker in the 20 and 30 minute tests, but still lighter than step 1 on the 5 and 10 minute tests. This shows empirically that there is a threshold level of moisture in the coated paper beyond which solarization is likely to occur.
If you see solarization regularly, first be sure that you are not over-exposing, and second pay close attention to the moisture level of the coated paper.
And finally, the entire calibration/profiling process affects the quality of the negative. That is the whole purpose. There is not one negative that is the highest quality for everything. The goal is to produce a negative that matches the characteristics of the printing process. That is the beauty of digital negatives and PiezoDN does it better, and with higher image quality, than any other method I’ve used (which is most of them including some inventions of my own). And it’s actually relatively easy once you get used to it!