Hi Michael,
My suggestion would be rather than limit inks in QTR to instead limit inks in PPETv2 and then create a new custom curve based on what you discover in ink limiting going through the entire linearization process.
I found that the Advanced Adjustments in QTR work significantly better with QTR designed curves rather than .quad files. So, I stopped using Advanced Adjustments sometime back in 2005. And I haven’t worked with QTR CurveDesign since, nor the Advanced Adjustments since we went all .quad. And its not a statement against QTR CurveDesign just that Piezography profiler went another direction 20 years ago and never looked back.
If you are curious - you could try limiting a starting curve in both and make comparative printouts to see how each handles ink limiting. In fairness to Roy, he may have made some changes so that .quads are limited in the same way his ink descriptor files are.
best,
Jon