This probably applies to any car with a bumper skin, but Porsche is the first time I've run across it. I bought mine used - the previous owners mounted the rear plate (no front plate) with sheet metal screws right into the bumper skin. It works, but not well, and the plate had loosened and rubbed the paint. A trip to the hardware store wandering around the nut and bolt aisle (grab the bag early and write down what you're getting - you'll never remember when you get to the counter) - 4 8-32 well nuts (expanding rubber sleeves), 4 8-32x1" stainless machine screws, and 4 #8 stainless finishing washers. I had to enlarge the existing holes to slightly over 1/4" to get the well nuts in. The plate is mounted securely, and the lip of the well nuts keeps the plate off the paint. Since I live in Vermont - I also had the pleasure of mounting a front plate bracket and plate on a virgin skin. The dimples are there, put some blue tape over them just in case, start small, and just like a band aid - drill into it... Hope this helps.