But I didn't realize you used the original lines of the car. While it might be great if it worked you might have to sacrifice the convenience of the oem bumper lines and do more of your own fabrication. Of course not something you planned on but like any project, its important to be flexible along the way.
Hey if it comes out sick I'll give you instructions on how to make a full mold to make fiberglass/polyurethane replica's! haha
Perhaps rather then just "filling in" the top grill, if you'd prefer not to... why not mold in an eBay upper grill insert? That might also give it a cleaner look because over-all the whole project seems very clean. The lip is simple, but aggressive, and there aren't any arbitrary vents or cuts made.
(Granted finding a 4 door upper grill insert is hard, since you're doing so much custom work, if the coupe grill isn't off width wise it might work. The top of the upper grill would be cut to accomodate the hood and the bottom part would then be open to being made into a more wedge shape to fit the contour of your idea.)
Oh another thing I realized, as stupid as this sounds, the picture of it temporarily fitted to your car might not be the most flattering angle. Maybe take a few more shots from standing height. I feel maybe the photoshopped picture looks better because of the stance of the car and the angle of the picture.
in addition it also doesn't seem like where you made your cuts you made a lip, like along the whole inside of the "cut out" grill there doesn't seem to be a lip around. This also gives it a hollow "obviously been cut" look. Are you planning on molding some sort of inner lip on?