The stock sports spoiler should cover all the holes for the nismo. The sports spoiler has CRAZY amount of holes take a look here. I took off my sports spoiler and installed a nismo seibon replica.
Here are all the holes (not necessary really....) With the 4 bolts, its more than enough just double side tape the rest... I can take better pics of my stock sport spoiler if u want. It is just sitting in my room.
I can get you more pics if needed.