These guys are correct sir. For our 3.5" Systems, the front lift is actually 4" +3/8 minus zero and the back lift is actually 3" +3/8 minus zero, hence the average of 3.5"!
It will very greatly depending on what kind of accessories you are running out back as well! Adding cantered loads is not a one to one relationship.
For example; if you add a spare tire carrier, full size spare and accessories hanging off the back of the vehicle, the back end will go down obviously, but most people do not realize the front will go up as well.
Hope that helps you out!