To add the wedge your boat needs to have reinforcements in the hull for the amount of drag the wedge adds. I dont think you can just "add" them. Correct me if Im wrong.
If you're adding to a Malibu you must go through a Malibu dealer. I understand that they require the hull id number. A wedge makes a huge difference in the wake - approximately equal to 1000 lbs of ballast.