Cranking up the Neutral Gray slider exaggerates the yellow cast appearing in printed highlights as the profile "compensates" for the blue paper substrate.
I'll grant that i1Profiler profiles show less yellow artifacts on OBA-heavy papers than did PMP5 (when Optical Brightener correction was disabled) or MonacoProfiler profiles. The problem is still there, however.
Using software-based OBA detection and compensation routines achieves almost the same final print quality as does the dedicated iSis OBC module.
We use our own OBA correction code, while Argyll and BasICColor Print have similar functionality.
Curiously, I have the opposite effect with the Neutral Gray slider. All way to the left (zero value) gives me the most yellowish cast with highly OBA-charged papers. When I set it to 100 I get I print more like the PM5 "Correct for Optical Brightener" feature and ArgyllCMS "-f" option. But i1Profiler seems to give us too subtle variation between 0 and 100, so it can't compensate enough fluorescent behavior of OBA-heavy papers. Some months ago I wrote that I would have noticed a high similarity between i1Profiler profiles and those ones created by PM5 with "COB" feature turned on. But more prints showed me I was wrong. In fact, subtle skin and sky tones are easily noticed between one and another profile, and those differences usually destroy our whitebalance finetuning, making it unpredictable.
So, while i1Profiler gives us the most beautiful profiles with mild or no-OBA papers, their yellow cast is unacceptable with b<-8 papers, specially for portraits and other whitebalance-critical jobs. PM5 is not much behind, so I still use it for these problematic papers.
Regarding to your OBA correction code, what does it consist? A software or worksheet that would manipulate measuring data file and correct inside values? Could you share it? Do you sell it? I think this would be the best thing, as someone could apply OBA compensation only when it is really required, preserving no-OBA paper profiles from blue filtering, and not only to perceptual but to every rendering intent.