I bought suction cups for my license plate so it's suctioned to my front windshield. I got rear ended not too long ago and it didn't move at all. Just my $0.02
Edit: These. They cost $2 and they work really good.
If you're going to put it in the windshield then this is the way to go.
If you have the plate tucked in the dash then it's partially obscured. You gotta have it a few inches up above the dash.
Use these suction cups to stick it to the inside of the windshield a few inches up from the dash where it's clearly visible and you'll have no problems. They have strong suction, it'll never fall off. I use these also.
I used these suction cups and just placed my plate in my windshield. Didn't want it scratching the dash. https://www.amazon.com/gp/product/B00032KBEA/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
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I put suction cups on a plate holder. I pull this out only when using metered parking (which is fortunately only a few times a month).
Cruiser Accessories 78410 Suction Cups, Clear, 4 pack – approx. 1” each https://www.amazon.com/dp/B00032KBEA/ref=cm_sw_r_cp_api_vG3Hzb2CWADSZ
They fit perfectly in the Model S front plate plastic holder, not sure if it works on other cars.
Agreed. Audis look stupid with front plates -- haven't used one for 10 years. But you can't park on the street in DC without a meter maid waddling by and seeing an easy ticket. On the rare occasions I have to, this sticks my plate in the window.