You're better off with the winch too high than not high enough. In your photo, if the bow eye was pulled up 3 more inches the eye would come in contact with the yellow trailer chock at the winch and then the line would not be pulling up so much. With the eye in contact with the chock every-time, would be a visual guide for placing the boat in the same position on the trailer everytime.
You have realized that different slopes of the launch ramp affects how the boat reacts to the trailer. By using different placements of the bow eye in relation to the trailer bow chock you have seen different things happen when the boat is hauled from the water. For every recovery to be somewhat the same the positioning of the bow eye to the trailer must be the same. The less strap from the winch which means less distance from the winch the less the bow eye or bow will move when you haul the trailer out of the water.
When you’re at the ramp the next couple times take note on what is happening with the boat the last 18 inches of recovery. The steeper the ramp the more you have to lift the bow up to that yellow trailer chock, which you think is over-stressing the bow eye in the hull.
Think of the water which is as close to level as possible on this earth, the hull sits somewhat level on this level water, but the ramp is not level, it slopes down away from the shore line so that it gets deeper and deeper. The bow of your boat sitting level on the water touches the front of the trailer, but the stern is floating 1 to 3 feet above the back of the trailer!
Now, to eliminate some of the stress on that bow eye when winching the boat onto the trailer you must have the trailer deep enough to float the hull up close to that trailer chock. If the trailer is not deep enough in the water the hull comes in contact with the front edge of the trailer bunks and you have to drag the bottom of the hull up these bunks which in turn lifts the bow higher out of the water. If the bunks are deep enough to reduce this friction then the winch will only be lifting the weight of the bow up out of the water which is much less stress on the bow eye.
How deep, deep enough to float the hull up to last 18 inches of winching would be perfect. Pull your strap out from the winch a little less than 24 inches and if you can not connect it to the bow eye then the trailer is not deep enough. If the ramp is so steep that the bow is under the winch for that less than 24 inch hook up then a bow roller would be off a great help in lifting the bow up towards the winch. A roller will create less friction in moving the hull forward and up than sliding up the bunks!
The winch must be high to do the lift and almost level with the eye in it’s final resting place to keep the bow from lifting higher and away from the winch when the stern finally comes in contact with the back of the bunks when the trailer is pulled out of the water.
Lifting the bow sinks the stern so the boat is no longer level and starts to mirror the trailer under the water.
Look at the attached photo of friends boat, it looks funny sitting bow down but, he can recover this setup in much shallower water because the hull and trailer matches the ramp when they both are in the water. This boat owner has been trailer sailing since 1965 and does small sail boat storage and repair. He takes care of about 7 boats a season in launching and recovery every season, so you can see in the photo of what 50 years of experience has done.
