If it was mine, I would probably do as Kurt has mentioned, but would try and keep the 420 from going all over the place. (I think one drop will cover a small plate.) I would try and mask the back with clear tape and make sure it is on tight, leaving the edge open. Then try and inject the stuff into the cracks, After it is set (over night at least), I'd remove the tape and hope for the best.
With luck it won't wick all over the limb, and only a little touch up around the area, to include feathering any edges in the original damage to keep any of it snagging.
Then give it a shot of your favorite clear rattle can or rub on finish, and it should be good to go.