Yeah, kind of screwed that before :P

com/Acrobot/Breeze/Utils/InventoryUtil.java

@@ -85,13 +85,17 @@ public class InventoryUtil {
     public static boolean fits(ItemStack item, Inventory inventory) {
         int left = item.getAmount();
 
+        if (inventory.getMaxStackSize() == Integer.MAX_VALUE) {
+            return true;
+        }
+
         for (ItemStack iStack : inventory.getContents()) {
             if (left <= 0) {
                 return true;
             }
 
             if (MaterialUtil.isEmpty(iStack)) {
-                left -= inventory.getMaxStackSize();
+                left -= item.getMaxStackSize();
                 continue;
             }
 

com/Acrobot/ChestShop/Listeners/PostTransaction/ItemManager.java

@@ -46,7 +46,7 @@ public class ItemManager implements Listener {
 
     private static void addItems(Inventory inventory, ItemStack[] items) {
         for (ItemStack item : items) {
-            inventory.addItem(item.clone());
+            InventoryUtil.add(item, inventory);
         }
     }
 }

plugin.yml

@@ -2,7 +2,7 @@ name: ChestShop
 
 main: com.Acrobot.ChestShop.ChestShop
 
-version: 3.50t0034
+version: 3.50t0035
 
 #for CButD
 dev-url: http://dev.bukkit.org/server-mods/chestshop/