cooltoy

I think that is the official one for the sports spoiler. But I thought it might give you an idea of how to build one. You can see how they use the bottom and the sides of the trunk as reference points.

I guess the way I would do it (and this is all just hypothetical).

I would first cut out a piece of paper in a similar fashion as pictured, but somewhat rough at first.

Than center it on the trunk, tape it and mark the reference points at the bottom and sides. Draw a center line vertically on the template.

Then place the wing on top of the paper, as it would attach to the car and trace the outline of the wing. Remove the template from the trunk and cut out the excess.

Than tape it to the underside of the wing using the outline created mark the holes and you are ready to go.

Another option I would consider is maybe putting some kind of fluid or gel on the edges of the holes, that would be non-damaging to the paint, and carefully placing the wing on the trunk in its intended location and hopefully get the liquid to show where the holes would be.

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