I am not quite sure how the number of crafable items affect lag, but I think someone said in thread that an increased number of items increased lag. If this is the case I would suggest removing items in such a way that only one item exist with a given ability, e.i. all iron helmets have the same ability and can be cosumized into looking like each other, therefore only one type of iron helmet is needed (same thing aplies to bronze, platinum, adamantium and mithril). Similarly the number of shields could be reduced to 3: small, large and kite. similarly the number of arrows could be reduced by saying only two types of feathers existed those that cause physicl damage and those that cause negative damage.
