Get a Saris Bones 2, it will go over your spoiler. I have a Miata and a RX 8 and and they both have a wing spoiler. They have a lifetime guarantee.
http://www.amazon.com/dp/B000BT30RK/ref=asc_df_B000BT30RK951855?smid=ATVPDKIKX0DER&tag=googlecom09c9-20&linkCode=asn&creative=380341&creativeASIN=B000BT30RK