I read on Sheldon Brown's website a long time ago that he suggested moving the cleats back, and I did so. I like it, it makes sense to me to not stress the calf muscles, and instead position the pedal closer to under the tibia, where the quads can exert pressure directly. Also I notice that when I don't think about it at all, just jumping on a bike and hammering (across an intersection for example) I generally end up with the pedal in this position instinctively.