Welcome to the Sue Nation
I guess I have lived by the no harm, on foul theory to long. I would expect for the damages to be fixed, But I would also want the cannon ball with the casts signatures to keep. Mythbusters is one of a couple shows I watch and with all the questionable things they have done, They do have a pretty good do it safe track record. Also I do believe if some one had gotten injured that would be a whole other ball of wax.