It can be done, but I would never do it to my truck. The problem you are gonna have, is that when a lift is designed to be 4", you dont wanna go to much higher than that, or you are gonna have issues. The main thing, is the control arms are only so long, and when you add the leveling spacer on top of the 4" lift, it is going to pull the wheels back a little, and throw everything out. To compensate this, you can get some longer control arms, and everything else should be fine. Not saying people dont do it, but it is definitely not the best way to get a few extra inches of lift.