Ideally, you want the weight to be as low as possible. The bunks should only balance the boat; the keel rollers are designed to carry the lions share of the load.
As for the bow eye, with the boat fully on the trailer it should be just below the stop. The reason? Because if you make a sudden stop, the bow of the boat can't ride up and over the tongue. Some tongues are welded and not adjustable for height.