I have two food shelves with 4 different items in them. Besides the max of all the rest of the storage methods like 6 Egg Machines and 5 Cabinets.
Does the fact that I have 2 independant Food Shelves answer your "stacking" question? I am making more of these shelves and working on the "Fridge". I will let you know the limit on those shelves when I reach it...