Instead of using BaseArmor try PlateChest. I'm not sure if that will work or not, but if it won't, in the Constructable add a line like
Code:
Layer = Layer.Chest;
I'm pretty it's Chest, but you might need to play with it a little bit. I'm not sure why what you have isn't working. I compared your script to ones I have for custom art and there's nothing different that would matter. All of my chests are BaseArmor as well.