It seems that POL will allow absolutely any item to be stacked as long as the client tiledata.mul says it can (note I said CLIENT, not server). This is a simple packethook that uses the entry Stackable 1 in tiles.cfg generated by uoconvert to check if stacking is allowed or not on the server side. This will allow you to reject stacking for items that could usually be stackable by changing just one entry in tiles.cfg on the server side for that item and it will also prevent players from being able to change their tiledata.mul to be able to stack whatever they please. Although note, this will not affect any existing stacks. This won't automatically break them up nor will it break the ability to be able to split them up. This packet will simply stop them from being able to create new stacks from previous individuals and stop them from adding to existing stacks.