I have an old 12' fiberglass canoe and I find myself scraping the bottom of it all the time. Either on rocks as I approach the shore, or on the pavement when I'm taking it off the car, or even as I carry it over obstacles in low water. I thought it might be a good idea to get a "liquid rubber" type product and put a coat on the bottom to protect it. Then it occurred to me that this might produce a lot of drag and make it much more difficult to paddle. Has anybody ever tried this or know if it might work?