Filler is a bandaid dude. You will drag those rudders against the bottom again, i'm guessing. You could make like a tail block that they sometimes put on long board surfboards and glass that on. You would have to grind down the sides of the blade near the repair so that after you fair the glass job down, the repair material will still be there.
Band aid also fine just not great at stopping the splitting once you hit again. If you had 1 spare rudder you could take some time doing the repair and not miss sailing days.