Do you need extra road clearance, view of road, or easier entry into car? If the latter two, you do know the seat has a generous amount of height adjustment? I max out mine for a better rear view (front view a bit improved), and better thigh support.
Messing with ride height with spacers can shorten tire and suspension life. I would consult an expert and not just add spacers.
Ditto what yitcoev said plus it will alter the handling characteristics most likely in a negative way, possibly make it less safe and would probably affect vehicle fuel efficiency by altering the aerodynamics.
Not criticizing but trying to give some food for thought before doing this to your vehicle. Realize its your car to do with what you want!