If it's a factory spoiler there will be holes in the under side of the trunk lid that are made to allow you to drill holes for the spoiler. Just take a quick measurement of the spoiler mounting area and see if there are corresponding holes in the deck lid. If not then Take some paper and tape it together so it's wide enough to stick out from under the spoiler. Put it down where you are going to place the spoiler and mark the edges of the trunk lid on the pattern to locate the pattern. Then put the spoiler where you want it and trace the out line on the paper. Remove the paper and using the tracing of the spoiler mark the spots for drilling then reinstall the pattern on the trunk and drill where you marked. A little work but it will get the job done right.