Hi,
Finally have 5 mins to comment on this one specifically! This is great to see, and I have been using similar numbers for quite a while now, actually probably closer to 15% but then it is not guided by any psychophysics experiments although I did play quite a bit with CIECAM02 and CAM16 at the time to get some hints.
Something to keep in mind though is that while a global colourfulness tweak tend to work fine, because the Hunt Effect is driven by the display Luminance increase, itself modulated by the tonescale, the tweak should be weighted somehow, e.g. shadows and midtones require different strength than highlights.
Cheers,
Thomas