Back when I was a kid, my Dad was faced with loading our boat by himself onto the roof of our station wagon. 14’ fiberglass rowboat that was heavy. He was a machinist by trade and devised a mechanism that fitted onto the trailer ball. It stood upright and had a tilting and swiveling U shaped receiver for the transom of the boat. He mounted a wheel onto the bow of the boat. Loading was simple- lift by transom and roll boat to car. Lift transom up into receiver. Go to front of boat and lift up. Now walk around car until boat is lined up above rack and lower onto it. Strap down boat.
Some guys came over to look at it once and then maybe 6 months later saw a commercialized version of it for sale…