Nicholas's paper he refers to both MGIV and Polymax. However, even though the last page of his paper specifically calls out MGIV MG RC, the gamma curves on page 6, generalised for 3-emulsion VC papers, show a double-dip in contrast when extreme 00 grade is used. I do not know if Nicholas intended this graph to be generalised, or how he has arrived at that model, but my experience, with MGIV WT, rather than MGIV MG RC, agrees with his findings, as it does with Bob's experience. All of that could be a coincidence, and I would welcome your more detailed analysis, very much.
post #44 on this thread, and if you have the time, also post #49 of this LFPF thread, in which I explained my thinking in more detail.
Indeed, I fully agree with you that once grade 1, or a higher filtration, in any colour system and by any means, split or not, has been applied, the curve straightens considerably, and this issue only affects the extreme grades of 00 and 0, and, as I mentioned in my earlier posts, not the final result that would have been achieved with an additional exposure—such as grade 5 added in a split-grade scenario. The point which I was trying to elaborate, perhaps ineffectively, was about a seemingly illogical progression of that problematic mid-tone, when it has been first laid using 00 alone, as observed by the worker, who later moves on to using a higher grade—for example: if you had printed a test sheet, as done in split-printing, using 00 alone, and another one, using grade 1, and if you happened to be lucky to have a picture rich in that problematic mid-tone, you would find that it did not differ, as you had expected, between sheet 00 and sheet 1, while the remainder of the print changed. In extreme, for a very soft, high-key print, it could be interpreted as the look that Bob has described.
Thank you, very much indeed, for helping me understand this issue in more detail, and I would be very grateful if you could let me know if you think my logic continues to disagree with yours, as I greatly appreciate your experience.