Not sure I have seen this posted here before, so I figured I would post up what I did. I live in a state with a front plate law..so it is a must unless you want to be harrased. Putting holes in the bumper was not an option, and since I go to shows, I wanted something easily removable. If someone else posted this..I apologize.
First off, start of with a stock plate frame-
Next, I got the below supplies..basically long ass toggle bolts and washers.
Assemble bolts in frame as shown below-
Next if your worry about the frame rubbing, apply some foam tape or similar to areas the frame can make contact.
Next, I applied some electrical tape to the toggles to prevent them from cutting into the back of the grille.
Next, put frame up to bottom grille, and align so toggle bolts slide into the very first slat of the grill. Then manuver the toggles to they are securly gripping the grille and tighten. Mine grip diagonally in the corner of the horizontal and vertical slats.
Securely tighten the bolts. You should be able to pull on the frame horizontally and vertically, and not have any give.
And here is the end result-
Also..in closing, if you don't trust the toggles for some reason..one other thing it appears you could do as a safe backup, is instead of putting the bottom tag bolts in..you could run a zip tie under the tag, and through the holes and grille.