Snapping an Extrusion Referring to the attached image, using a simple extrude and scale workflow, is it possible to snap the upper extrusion so it matches the size of the lower one? I thought this would be quite simple but I just can't seem to work it out....
With the top face deleted and vertices selected ...


Set Pivot to Median
Set snap to Vertex and Active, and set it to influence Scale. Check 'Project on to Self'. 
With cursor close to Active (white) vertex Extrude E Scale S Limited Axis ShiftZ and snap the active vertex to the one below it.




(Holding Ctrl while dragging toggles the 'Snap' state.)