Add a vertical ASA to your Sterling with this CNC-machined aluminum extended rail. 
 
Using an Automag vertical ASA, you can now run "VSC" with a bucket changer. Or, if constant air is your thing, add an inline regulator - the easiest way to control velocity on some of the older models. 
 
Select "Arrow" to fit a modern Sterling, or "Classic" if you have a potmetal frame and plastic rail.