Here are the instructions that I used. I did not write these instructions but these and some great photos can be found on the Planet-9 forum. Just look for "The Dreaded Front License Plate":
Basically, I went to the hardware store and bought some T Nuts, some stainless steel 3/8" screws and washers, some plastic spacers, and some 3M emblem tape from the auto parts store, hopefully you can see where this is going...I also gave the bumper a quick wipe down with IPA to make sure I have good adhesion.
Basically using this method I can attach the bracket to the bumper with emblem tape, it won't come off, even in winter driving, and if I need to remove the bracket to wax the car, I can easily do so. If I ever move to a place that does not need a front tag, or the next owner wants to run around naked up front, I can take it all off without leaving any marks, and all I will have wasted is $3 in hardware from Ace and 10 minutes of my time.
After cleaning the bumper with IPA I install the t nuts, spacers, screws and washers into the factory bracket, remove the adhesive backing then carefully position it in the correct place on the bumper. Then I remove the screws, remove the bracket and make sure that I firmly press the T nuts into the adhesive and the bumper so there is good contact. Then I re-installed the bracket and snug up the screws and make sure everything is straight and firmly attached. Then I attach my license plate..."
My plate has been on my car for 1.5 years Now with no problem. I just occasionally check it to make certain.
I hope this helps.
I thought I should post a photo of the finished product: