How wide is this grill?
What do you mean by bent? Do you have to lay it on the table to see it? Is it 1/16 , 3/8 ..... or 3/4 bow ? Take a picture .
I use mine all the time on a 22 " kettle (several times a week even) and have had it bend a little from to much weight but it did not stay bent nor did it.
Maybe you should spread your birds out away from the center. That will distribute the weight better.