for starters, you can set color space to "auto" and set color to get red luminance as close as possible and the secondary hues a low as possible overall
later on, you can use "custom" color space to dial in LCH for each primary and secondary
QuickView Grayscale.pdf 58.2724609375k . file
You do but you get Red as close as you can first.
L = Luma Y
C = Saturation y
H = Hue x
Primaries get Luma matched, Secondaries get Hue matched... and then have fun balancing back and forth for hours until it's all as perfect as can be (at this point a little OCD is required ).
Adjust Color Gamut.pdf 116.76171875k . file
Gamut After.pdf 115.986328125k . file
Enhanced Gamut .pdf 116.4111328125k . file