Wow, that is an outstanding way to repair the grille. Hmm...I wonder if a little fiber glass sprinkles mixed in would help with the strength even though it looks as strong as new.
I was glad to see that after about twenty minutes you could bend the repaired tab and the grille would flex a few inches down from the repair. very strong. I think you could use some fiberglass, but this way after you sand and prime the repair will be invisable