I have an older boat and the same problem with the keel wearing from parking on the bank. It's either repair the glass or cover it up. I had the same idea a year or so ago and checked with a place on Glasgow that sprays the truck beds, They had never heard of doing it on boat hull or keel, and said they wouldn't guarantee it to stay on. I would still be interested in this if I knew it would stay put as the forward keel isn't in the water at planing speed anyway. Anyone out there know any more on this???????