I think that the answer to where you put your hand is the same as where you would put the shelf. You put the shelf where you can get good arrow flight, and good fletch clearance. This will vary from bow to bow, depending on the bow's tiller.
You would like your nocking point to be about 1/2 - 5/8" above your "shelf" which is your knuckle. So try various locations and see where the arrow flies best. This assumes those locations are repeatable, and you can hold a bow square on your knuckles to find a nock point.
If you have no way of repeating your grip location from shot to shot, and don't plan to use a nock point, then I think, like Luke Skywalker, you just have to trust the force.