Post a picture. I believe I know the one you are talking about (see below)
If its the one I am thinking it is then most folks will cut it in half and then shorten it to the needed width and rivet it back together using the section they cut out to reinforce the back.
I know for a fact that Ginster86roc has a front spoiler (not sure if its the same one you are talking about) and there are some good pictures up of his installed somewhere on this site. I just found this one ... if you look in the center you see what I recall are rivets
I found this one.
Calling Ginster86roc ......