Thank you again for this tutorial.
I added a slight modification to help with the window dragging:
in Inventory.cs, under create layout I changed this line for the background height:
inventoryHeight = rows * (slotSize + slotPaddingTop) + 25;
...and changed this for the slots:
slotRect.localPosition = inventoryRect.localPosition + new Vector3((slotPaddingLeft * (x + 1) + (slotSize * x)) , (-slotPaddingTop * (y + 5) - (slotSize * y)));
...then did a padding of 5 left and 5 top and it gave me a very thin, but effective top border on the inventory.
One could probably also add a GUIText to the top of the inventory window to help distinguish each one apart.
Amazing tutorial - absolutely amazing.