Thanks for all the responses and all the great ideas.
I probabaly thought about this way too late. My cowl vent grill is all ready to have color sprayed on so it's too late for welding any connections. If I did do anything, it would have to be done with adhesive.
I tried playing with a little piece of black aluminum window screening on a spare cowl vent grill at home and it looks pretty obvious. Too obvious! But it wasn't installed on the car and had some light coming through from the back. Maybe installed on the car with no light coming from behind, it will look different.
I will try it for real at the shop where the car is next week and go from there. If it stands out like a sore thumb, I'll proabably scrap the idea. I was hoping I could do it without it being really noticeable. Probably, 99.99% of the Camaros out there don't have something like this and fair OK.