Thanks for the replies. My Cooper is a 2002 model so it is not the new R56.
I have seen an Aero spolier that was fitted on a Cooper and, as you say Richard, it looked quite beefy, but there is something with the shape of the S spolier that I think is very cool. I have decided to go for an S one, so I will keep you posted on how the development goes.
I really hope I does not destroy "Trigger"

when drilling the holes, this car really triggered me into the world of Mini
One final question, I guess I have to remove some plastic parts (just beneath the spoiler on the inside, or is it the plastic frame surrounding the window that has to come off a bit?) so the bolts is possible to attach to a screw so it stays in place.
I looked at a Cooper S at the dealers site, but you could not see the bolts inside the hatch just beneath the spolier. Anybody with a suggestion to that?