Apparently some people just use the 4 holes when changing from the lower spoiler to the extreme to save drilling more. The threads I have read in the past about it say that no one has a problem with it, especially if you use strong adhesive tape as well as the bolts.
It uses the same 4 off fixing holes as the small spoiler, you can easily drill the other 2 inboard ones by laying masking tape along the boot edge. Use the 4 off existing holes to line the extreme one in position and mark around the remaining 2 off studs. Drill, deburr, clean and protect, job done.