Can't figure out how to use SyncListStruct

I've been searching around and looking at other people who have got it working, but I can't figure out what is wrong in my scenario. My game has multiple characters with belts, and I want the server instances to manage the belt configuration and sync that to clients.

Declaration of my SyncListStruct type:

Code (CSharp):

1.     public struct BeltItemSyncData
2.     {
3.         public int ItemID;
4.         public int Quantity;
5.         public float Cooldown;
6.  
7.         public BeltItemSyncData(BeltSlotMeta beltSlotMeta)
8.         {
9.             this.ItemID = (int)beltSlotMeta.ItemID;
10.             this.Quantity = beltSlotMeta.Quantity;
11.             this.Cooldown = 0;
12.         }
13.  
14.         public BeltItemSyncData(int itemID, int quantity, float cooldown)
15.         {
16.             this.ItemID = itemID;
17.             this.Quantity = quantity;
18.             this.Cooldown = cooldown;
19.         }
20.     }
21.  
22.     public class SyncList_BeltItems : SyncListStruct<BeltItemSyncData> {}

Instantiation of the SyncList_BeltItems type in my Character class:

Code (CSharp):

1.     [RequireComponent(typeof(NetworkTransform))]
2.     [RequireComponent(typeof(CharacterController))]
3.     public class CharacterInstance : CharacterControllerManager, ICollidable
4.     {
5.         ...
6.  
7.         public SyncList_BeltItems BeltItems = new SyncList_BeltItems();
8.  
9.         ...
10.  
11.         // Use this for initialization
12.         public override void Start()
13.         {
14.             base.Start();
15.  
16.             BeltItems.Callback = OnBeltItemsChanged_Internal;
17.             ...
18.         }
19.  
20.         protected virtual void OnBeltItemsChanged(SyncListStruct<BeltItemSyncData>.Operation operation, int index)
21.         {
22.             //BeltItemSyncData beltItem = BeltItems[index];
23.             //ItemID itemID = (ItemID)beltItem.ItemID;
24.  
25.             switch (operation)
26.             {
27.                 case SyncList<BeltItemSyncData>.Operation.OP_DIRTY: // An item property changed
28.                     Log.Add("PlayerInstance.OnBeltItemsChanged(): An item property changed");
29.                     break;
30.                 case SyncList<BeltItemSyncData>.Operation.OP_SET: // An item has been replaced by another
31.                     Log.Add("PlayerInstance.OnBeltItemsChanged(): An item has been replaced by another");
32.                     break;
33.                 default:
34.                     Log.Add("PlayerInstance.OnBeltItemsChanged(): Unsupported SyncListStruct<BeltItemSyncData> Operation: {0}", operation.ToString());
35.                     break;
36.             }
37.         }
38.  
39.         private void OnBeltItemsChanged_Internal(SyncListStruct<BeltItemSyncData>.Operation operation, int index)
40.         {
41.             OnBeltItemsChanged(operation, index);        
42.         }

And when I walk over an item on the ground, I update the belt (on the server), but I don't get any kind of output telling me the belt has been updated on the client. (OnBeltItemsChanged)

Code (CSharp):

1.         public void OnItemTouched(ItemInstance itemInstance)
2.         {
3.             // Only the server instance of the character can pick up items.
4.             if (!isServer)
5.             {
6.                 return;
7.             }
8.  
9.             ItemMeta itemMeta = ItemManager.Instance.GetItemMeta(itemInstance.ItemID);
10.  
11.             // Do we have room?
12.             int slotIndex = GetSlotIndexForItem(itemMeta);
13.             if (slotIndex != -1)
14.             {
15.                 BeltItemSyncData oldItem = BeltItems[slotIndex];
16.                 BeltItemSyncData newItem = new BeltItemSyncData(oldItem.ItemID, oldItem.Quantity + 1, oldItem.Cooldown);
17.                 BeltItems[slotIndex] = newItem;
18.  
19.                 NetworkServer.Destroy(itemInstance.gameObject);
20.             }

Sorry for posting large amounts of code, hopefully its not too hard to walk through. Any idea what I'm doing wrong? The item is being destroyed so I know this code is being executed on the server, but updating my sync list struct doesn't call OnBeltItemsChanged_Internal.