I don't think this question belongs in the general tread on the D810.
First let me admit I have read Thom Hogan's manual for the D800. I do not have his D810 manual yet. Second let me admit that my eyes glaze over after only two or three paragraphs. And last let me admit that I have never used the D810 Custom Setting menu items.
Now, with that context, "how do I maximize the use of Face Detection on a D810?" In the past I used single point focus and focused on the nearest eye. It seemed to work in "P", "A" and "M" modes. But I wonder if there is a better, more automated way.
Robert M. Poston: D4, D810, V3, 14-24 F2.8, 24-70 f2.8, 70-200 f2.8, 80-400, 105 macro.