Depends on what pattern I happen to be using...and how much axis tilt I need...
My normal one I keep the ball just inside my left heel (an inch or a couple) and vary stance width and weight distribution....narrower stance and more forward weight for more descending strike.
If I am using a varying ball position with respect to the left heel....I don't really ever put the ball back of center....but I vary stance width as well.
...
Whichever way works best for you and you're most comfortable with you should choose...
And whatever way you happen to choose it's good to understand that when you change ball position and those other factors (stance width, weight distribution) what you're really doing is changing the ball position in relation to the left shoulder. (that's why it works kinda the same...not exactly the same tho)
The left shoulder of course is the low point of the swing.....it's the centre of the circle.....and the left arm is the radius of that circle.....thus right under the left shoulder is as low as your hands can be....the low point of the circle.
Here's a picture I took from Paul Smith at iseekgolf:
Johnny Miller, Jack Nicklaus, and Ben Hogan are the 3 most notable golfers who have used an "always off the left heel" ball position.