Easy once you have measurements! Thanks chtcuda!
In case the photo get lost in the future here are my notes....
4 bracket holes are 3 3/8th to 3 1/2 inches above the bottom edge.
The first hole is 13 inches in from the left edge and the 2nd hole is 8 1/2 inches from the 1st.
Repeat from the right side 1st 13inches 2nd 8 1/2 from 1st.
When installing the brackets in the spoiler the bolt rests in the notch and is held in by the flat nut, there is a small amount of play for adjustment, I think that is why the nut is so large....