Hi NTL - The spindle mount only stiffens the bottom of the plate. Once the Z axis moves down past a certain point its only 1/2" thick plus the rails in stiffness. Thats why people are recommending reducing the Z axis travel or adding outside webs to the Z plate or sled as Jake is calling it. If the Z axis can be organised to take advantage of the spindle stiffness then that's very good. Peter