For fully grown cities I often run into problems with available storage. Buildable storage in the game is limited and expensive. There are 44 different goods (although food does not count.) Having only one cargo load (= 300 pieces in marathon) of each good in storage would probably already exceed buildable storage. Especially when allocating and refining ALL the types of raw materials in a hub city with good food supply and several factories, storage is almost always at it's limit. Therefore I had the idea to add some extra storage to all the productive buildings, representing factory internal storage for raw materials and produced goods. This probably can be done by a simple xml-editing (<iYieldStorage> in CIV4BuildingInfos.xml). I also thought about cloning the highest warehouse with higher storage value so that the player could build kind of additional storage expansions.