I have a 2014 A-6 with the ribbed, curvilinear grille. I live in a state that doesn't require a front plate so I never got the grille insert. I tried to install a tag using industrial strength velcro as suggested in posts here and it failed. Someone else suggested rare earth magnets but posted no install instructions. I ordered nine magnets from a local supplier (they are cheap). I placed three inside the tag holder. Then I placed another three on the outside of the tag holder against their corresponding mates. I assembled the tag inside its holder and positioned the plate against the grille. I then reached behind the grille and placed the last three magnets snugly against the mating three on the other side of the grille. Result is a solidly installed weatherproof plate that looks pretty dam good and I didn't have to permanently mar the grille by drilling holes in it.

 

Rare earth magnets, huh. Since those are supposed to prevent arthritis, let us know if they prevent CELs and other OOOO issues.