you need at least 6 holes (3 each side).
i afraid that 6 holes will not enough to hold the wings so i did another 8 holes for the hatch plate

but from the bottom of my heart, if you dont want trouble with cops pull you over, keep the nismo wings. i am in the middle of everythings. i want to put the wings on everyday but i dont want anymore ticket so the APR just sit in my garage. (and i did drill 6 holes before i realize that it was too late to sell the wing. 6 big a$$ holes is already there. in my own desperation, i make another 8 .)
BE carefull when drilling holes my friends.
DSC_0753 by
dkinghl, on Flickr