I think I know what you're talking about. If possible, I would try it on scrap before buying any amount of it. I doubt that you could sand it, from what I remember, it's very rubbery. I imagine it would be tough, but it would do the opposite of what graphite does. Rather than encouraging the boat sliding over a rock, it would reeaally dig in. I think it would wear the Rhinoliner off pretty fast, even though it is tough. Maybe you could use a strip of aluminum, or even better, some high quality stainless steel. But beware of using any metal that you got a "deal" on. Cheap stainless steel often is only stainless while inside in Arizona. You can probably get some strip from West Marine along with some screws. I think it will work, and I might even use it on my kayak.

If you want to go high-tech, get some titanium, though it will probably be hard to bend around the stems.

Just an opinion, if anyone disagrees, don't hesitate to tell me.