Had a couple of questions in regards to this.
Spoiler should be a direct fit on the 09/10 models.
Pics from 2011 boot
Holes 1
Holes 2
Boot from a 2011 STi sedan
Holes
A member from here has also installed the same spoiler on his car.
Clicky
Few pics of the mounting holes found on the STi spoiler can be found
here.