I ordered my car with no front plate holes drilled in the bumper, but my state requires a front plate, so I've been pondering options for at least a year and reading the numerous threads around here re. front plate mount options.
I have 3M clear stuff on the front clip, which is a must on these cars considering the huge amount of bugs that stick to the front bumper, so I didn't want to scratch up the 3M film either.
I ended up installing the factory plate mount upside down, but with the bottom ON TOP of the chin spoiler. Two five inch toggle bolts hold the plate to the lower grille with a very slight upward incline.
Running this project by my local trusted hardware store guru, he suggested using two rubber fender washers behind the grille and in front of the toggle clips. This not only keeps the rear of the plastic grille from getting scratched up, but provides a sticky surface to capture the toggle clips and keep them from turning, and keeps the toggle bolts centered in the square grille section. This way I don't need tubing on the threaded length of the toggle bolts to keep them from scoring the grille squares, they are centered inside the squares.
To be totally over-anal, I found some nylon bushings in the parts drawer at the hardware store, and ran the toggle bolts through them with a lock washer on top behind the bolt head so there is a little spring tension on the bolts. With that and the rubber fender washers on the back of the mount to provide grip, this mount is super solid with only two bolts holding the plate mount to the grille.
The benefits of this whole setup are NO DRILLING, and can be removed leaving no holes and no scratches.
I considered the fact that this mount would restrict airflow, but found that after I mounted this setup, there is a good three inches or more of space behind the factory plate mount, so there is no reason the air cannot flow around the back of the plate. All in all a good and cheap solution.
To retain the front plate, I found two blackened Allen head bolts, and used a brass nut on the rear to thread them through the holes. This way I did not have to force the factory license plate bolts through and into the plastic of the plate mount gouging it up. Again all removable this way.
I have spoken and found this to be good!