Yeah that look tight, but I would have taken it to another level. I wouldnt want to leave any trace of silver on the exterior and I just didnt want to go to that extreme.
As for the Nismo spoiler, I actually have the Seibon NSM full carbon fiber version which is a bit cheaper. There is also an EVO-R replica out there now and theres even a new thread where somebody purchased a replica off of ebay for like $250. Not sure if he has installed it yet, Ill try to find the thread.
Here it is:
Nissan 370Z 09-11 Duraflex N-2 Wing Spoiler
Its tjlazer who is doing pretty much a full Nismo conversion.