I agree with what EnderGhost said. I like that it's simple and doesn't have all the fluff that SilkSpawners has. We wanted it only to give spawners from crates. That being said a way to set a % chance for a drop and we might use it for for allowing players to mine them with silk touch as well. We'd need to be able to set a very small % because we have custom terrain that has a lot of castles, dungeons etc that have many spawners so 100% chance is way too OP.