I had a similar problem when I removed my original grill and tried to fit a second one I had bought off Ebay. It appeared to kink in the centre upper. I tried everything to get it to fit and I knew that the front had not been changed so it had to be the grill.
I found that it required very little change on the outer edges to make the kink lessen in the centre. When fitting it I was using tape to avoid scratching the paint work and realised that if I put double or tripple tape on the outer edges the kink almost, almost disapeared. It became one of those things that your eye is drawn to when you know that there is a blemish on your car!!! Most would not have seen it but I always did.
Unfortunately, I was never satisfied with the final outcome and ended up getting my original grill repaired and re-chromed at more than the replacement grill and fitted it with out a problem.
I suggest you try the tape method before anything else.
Garry