I've got a OEM American smoothed grill and carry 2 plates, 1 on the car and 1 in the boot. 1 is held in place with magnets, the other is held in place by double sided suction cups.
I have 16X 20mm X 3mm N35 Neodymium magnets, 8 on reverse of the plate and 8 on the reverse of the grill. I don't have any pics of the magnets attached to my car but there is guide on them....
~~ Clicky here ~~Magnets i bought are from eBay.....
~~ Clicky here ~~And with the suction cups on mine...
Any problems, pop me a PM!