I don't use clipless, but I do alter my toe clip set up and learned:

one inch forward of the center of you foot is my best position as long as I'm using a hard soled shoe.

On platforms I use my toe, but my road bike is set up weird to give me better spin, so it's the only bike I push with the center of my foot.
Also, toe gives more strain and you can't work the upper muscle on your knee. I found this out when I trained on my toe clips and my knees killed me because I was lifting in the center of my foot.


For clipless, I would set it to the center so that when you push down, all the slack is out and you move my one inch forward