Aparently when you cook your mod the unreal editor copies many files that you just don't need. You can delete any ".bin" or ".upk" file that you didn't make your self. This includes all the files with "shader" in the title as well as the copied default goatgame ".upk" files that are in the "packages" folder. I am not sure why these get packed too, I guess it packs anything that you use even if it's a duplicate from the default. This makes me suspect that it's incase you are changing the default upk's as a "skin" or alternate model.