Since the origin of the cube was in 0,0,0 my method was:
Shift+C to put the 3D editor in 0,0,0
In the NumPad click 5 to put an orthographic view and then 9 to view the model from the bottom
Click the very center of the cube while looking from the bottom to put the 3D editor at the bottom of the cube and at the center of it
Choose 3D selector pivot point and scale

