I determined the location on the Slipper by how it fit my winch and bow stop.
Wanted the eye well above the hulls waterline to avoid leaks and low enough
that the line of pull to the winch was slightly upward to avoid stressing the hull
during retrieval and while sitting on the trailer. If the eye is too high, and the winch
can't be adjusted to fit the location, then the tension created by the winch
will pull down on the bow, causing a load that can hog the hull. I see that problem a lot
on older fiberglass hulls. A download on the bow causing an upward bend in the
line of the keel where it hits the forward roller.
note the upward line of pull from the eye to the winch...