For clarity, when you say don't adjust RGB low end at 30% white, leave the RGB settings for the low part of a 2pt grayscale at the display's default settings. Then go about adjusting the 10 pt grayscale if needed. If you've got the capability, verify using 20 pt grayscale as sometimes the inbetween points of a 10 pt adjustment goes out more than you'd expect. For example, if you adjust 20 and 30% levels to merge RGB, you may find that 25 R or G or B pops up/down away from the other two. You might do better with less or more adjustment to keep the average where you want it.
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