diff --git a/EOLib.IO/Map/Matrix.cs b/EOLib.IO/Map/Matrix.cs
index 553b51a9c..bfb05f807 100644
--- a/EOLib.IO/Map/Matrix.cs
+++ b/EOLib.IO/Map/Matrix.cs
@@ -30,7 +30,7 @@ public Matrix(int rows, int cols, T defaultValue)
             Fill(defaultValue);
         } 
 
-        public Matrix(Matrix<T> other)
+        public Matrix(IReadOnlyMatrix<T> other)
             : this(new T[other.Rows, other.Cols])
         {
             for (int row = 0; row < other.Rows; ++row)
diff --git a/EndlessClient/HUD/Inventory/InventorySlotRepository.cs b/EndlessClient/HUD/Inventory/InventorySlotRepository.cs
index 1f1b6811a..b3da1b47a 100644
--- a/EndlessClient/HUD/Inventory/InventorySlotRepository.cs
+++ b/EndlessClient/HUD/Inventory/InventorySlotRepository.cs
@@ -2,17 +2,22 @@
 using EndlessClient.HUD.Panels;
 using EOLib;
 using EOLib.IO.Map;
+using System.Collections.Generic;
 
 namespace EndlessClient.HUD.Inventory
 {
     public interface IInventorySlotRepository
     {
         Matrix<bool> FilledSlots { get; set; }
+
+        Dictionary<int, int> SlotMap { get; set; }
     }
 
     public interface IInventorySlotProvider
     {
         IReadOnlyMatrix<bool> FilledSlots { get; }
+
+        IReadOnlyDictionary<int, int> SlotMap { get; }
     }
 
     [AutoMappedType(IsSingleton = true)]
@@ -20,8 +25,12 @@ public class InventorySlotRepository : IInventorySlotProvider, IInventorySlotRep
     {
         public Matrix<bool> FilledSlots { get; set; }
 
+        public Dictionary<int, int> SlotMap { get; set; }
+
         IReadOnlyMatrix<bool> IInventorySlotProvider.FilledSlots => FilledSlots;
 
+        IReadOnlyDictionary<int, int> IInventorySlotProvider.SlotMap => SlotMap;
+
         public InventorySlotRepository()
         {
             ResetState();
@@ -30,6 +39,7 @@ public InventorySlotRepository()
         public void ResetState()
         {
             FilledSlots = new Matrix<bool>(InventoryPanel.InventoryRows, InventoryPanel.InventoryRowSlots, false);
+            SlotMap = new Dictionary<int, int>();
         }
     }
 }
diff --git a/EndlessClient/HUD/Inventory/InventorySpaceValidator.cs b/EndlessClient/HUD/Inventory/InventorySpaceValidator.cs
index 54766b72c..a69af1f8a 100644
--- a/EndlessClient/HUD/Inventory/InventorySpaceValidator.cs
+++ b/EndlessClient/HUD/Inventory/InventorySpaceValidator.cs
@@ -5,6 +5,7 @@
 using EOLib.IO.Map;
 using EOLib.IO.Repositories;
 using Optional;
+using Optional.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using System.Windows.Documents;
@@ -42,6 +43,31 @@ public bool ItemFits(int itemId)
 
         public bool ItemsFit(IReadOnlyList<InventoryItem> outItems, IReadOnlyList<InventoryItem> inItems)
         {
+            var slotsCopy = new Matrix<bool>(_inventorySlotProvider.FilledSlots);
+
+            foreach (var item in outItems)
+            {
+                var itemData = _eifFileProvider.EIFFile[item.ItemID];
+                _inventorySlotProvider.SlotMap.SingleOrNone(x => x.Value == item.ItemID)
+                    .Map(x => x.Key)
+                    .MatchSome(x => _inventoryService.ClearSlots(slotsCopy, x, itemData.Size));
+            }
+
+            foreach (var item in inItems)
+            {
+                var itemData = _eifFileProvider.EIFFile[item.ItemID];
+                var itemFits = _inventoryService
+                    .GetNextOpenSlot(slotsCopy, itemData.Size, Option.None<int>())
+                    .Match(some: slot =>
+                    {
+                        _inventoryService.SetSlots(slotsCopy, slot, itemData.Size);
+                        return true;
+                    },
+                    none: () => false);
+                if (!itemFits)
+                    return false;
+            }
+
             return true;
         }
 
diff --git a/EndlessClient/HUD/Panels/InventoryPanel.cs b/EndlessClient/HUD/Panels/InventoryPanel.cs
index 7c89b0b5b..c87fd8238 100644
--- a/EndlessClient/HUD/Panels/InventoryPanel.cs
+++ b/EndlessClient/HUD/Panels/InventoryPanel.cs
@@ -50,7 +50,6 @@ public class InventoryPanel : XNAPanel, IHudPanel
         private readonly IActiveDialogProvider _activeDialogProvider;
         private readonly ISfxPlayer _sfxPlayer;
 
-        private readonly Dictionary<int, int> _itemSlotMap;
         private readonly List<InventoryPanelItem> _childItems = new List<InventoryPanelItem>();
 
         private readonly IXNALabel _weightLabel;
@@ -101,7 +100,7 @@ public InventoryPanel(INativeGraphicsManager nativeGraphicsManager,
                 AutoSize = false
             };
 
-            _itemSlotMap = GetItemSlotMap(_playerInfoProvider.LoggedInAccountName, _characterProvider.MainCharacter.Name);
+            _inventorySlotRepository.SlotMap = GetItemSlotMap(_playerInfoProvider.LoggedInAccountName, _characterProvider.MainCharacter.Name);
 
             var weirdOffsetSheet = NativeGraphicsManager.TextureFromResource(GFXTypes.PostLoginUI, 27);
 
@@ -206,7 +205,7 @@ protected override void OnUpdateControl(GameTime gameTime)
                 {
                     var itemData = _pubFileProvider.EIFFile[item.ItemID];
 
-                    var preferredSlot = _itemSlotMap.SingleOrNone(x => x.Value == item.ItemID).Map(x => x.Key);
+                    var preferredSlot = _inventorySlotRepository.SlotMap.SingleOrNone(x => x.Value == item.ItemID).Map(x => x.Key);
                     var actualSlot = _inventoryService.GetNextOpenSlot(_inventorySlotRepository.FilledSlots, itemData.Size, preferredSlot);
 
                     actualSlot.MatchSome(slot =>
@@ -484,38 +483,6 @@ private void HandleItemDoneDragging(object sender, InventoryPanelItem.ItemDragCo
             {
                 _sfxPlayer.PlaySfx(SoundEffectID.InventoryPlace);
             }
-
-            #region Unimplemented drag action
-            /*
-            if (TradeDialog.Instance != null && TradeDialog.Instance.MouseOver && TradeDialog.Instance.MouseOverPreviously
-                && !TradeDialog.Instance.MainPlayerAgrees)
-            {
-                if (m_itemData.Special == ItemSpecial.Lore)
-                {
-                    EOMessageBox.Show(DialogResourceID.ITEM_IS_LORE_ITEM);
-                }
-                else if (m_inventory.Amount > 1)
-                {
-                    ItemTransferDialog dlg = new ItemTransferDialog(m_itemData.Name, ItemTransferDialog.TransferType.TradeItems,
-                        m_inventory.Amount, EOResourceID.DIALOG_TRANSFER_OFFER);
-                    dlg.DialogClosing += (o, e) =>
-                    {
-                        if (e.Result != XNADialogResult.OK) return;
-
-                        if (!m_api.TradeAddItem(m_inventory.ItemID, dlg.SelectedAmount))
-                        {
-                            TradeDialog.Instance.Close(XNADialogResult.NO_BUTTON_PRESSED);
-                            ((EOGame)Game).DoShowLostConnectionDialogAndReturnToMainMenu();
-                        }
-                    };
-                }
-                else if (!m_api.TradeAddItem(m_inventory.ItemID, 1))
-                {
-                    TradeDialog.Instance.Close(XNADialogResult.NO_BUTTON_PRESSED);
-                    ((EOGame)Game).DoShowLostConnectionDialogAndReturnToMainMenu();
-                }
-            }*/
-            #endregion
         }
 
         private static IEnumerable<int> GetOverlappingTakenSlots(int newSlot, ItemSize size, IEnumerable<(int Slot, ItemSize Size)> items)