I looked at the Roush rear deck spoiler. I ended up installing the rear spoiler from the 2010 GT-500 track pak. This is for my 2010. Then NO holes to drill ! The same oem 4 holes are used for the oem tiny spoiler, the GT-500 spoiler and also the CS spoiler
(elevated pedestal). The track pak version comes with a gurney flap. I was at the Roush dealer one day..and compared the 2012 GT-500 spoiler to the Roush 2010 427R spoiler same as you have)..and the GT-500 is exactly 1" deeper. BTW. the gurney flap with it's tiny lip actually works. The regular 2012 GT-500's also come with the same flap..but with no lip.
The Roush rear spoiler looks cool.... but I didn't trust myself drilling holes to handle the Roush 3 piece spoiler. All 3 x versions of the Ford spoiler are all just 1 piece.