@mtc
IMO, install a lip spoiler on the bootlid. That way, you will not spoil the cars bootlid by drilling holes and it will look really nice, especially on a black car with nice alloys. Ditto for a body kit if you ever decide to fit one, just fit a lip spoiler on the front bumper and the rear to change the shape a bit, nothing over the top. It'll look professionally tuned (y).
A low profile spoiler like the ones above will not spoil the cars aerodynamics either...
Cheers and drive safe,
Sami