The method described works fine and the boat just floats off the trailer. Do remember to undo you restraining straps or the trailer will remain suspended underneath the boat to the enormous amusement of bystanders. Also tie the rope on both ends before unhitching to avoid similarly hilarious results. I have found that fresh water is harmless and that salt does the damage. I like the idea of a launching trolley but how to get it off the road trailer and onto the trolley?