Well he hasn't painted anything yet, the black paint is all photoshopped.I can't tell in the pic, do you have the roof painted also? If not, it should be.
And I like the lip how you have it, seems to tie everything together. If you just did the middle part of the lip, it would look unfinished, and as if something was missing.
Will you be doing the trunk lid also? I think doing the trunk lid, and possibly the "diffuser" would make it nice.