If the original coats of gluvit didn't solve your problem, I doubt more will either. I suspect you will want more layers of fiberglass with the gluvit. The top layer is going to get rubbed, and you need something there to take the rubbing. I think you'll want something with some more strength to it, which means glass.

On my old wood boat, we put a layer of 25 oz woven mesh for the protection layer, saturated and laid with epoxy. Then we put a coat of epoxy mixed with graphite for the final coat. This boat ran over the rocks for eight years with no need for repair. You can get this stuff from the wooden boat shop in Seattle.