How close to the drying floor do you run your stirrators?

We were told to run them no closer than 16 inches...........but it seems that we get too much 10% corn at the bottom.........the stirrators are obviously not picking the corn up and moving it higher.

Seems that we ought to weld on some extensions, and put the stirrators within, say, 6 inches.

(30ft bins, 3 stirrators)

What say you? 

THanks.