Sounds good, but then the plate would be above the grill and you'd see the mounting bracket below it which would look c**p 
  
No, you'd take the mounting bracket off it  
  
 
  
  
  
It's the plastic bit that's part of the bumper that will still show. Arrowed in the attached picture. 
  
There is a metal bracket that screws over this for the JDM number plate, but obviously they are a different shape completely. 
  
Still looking for a better way   
  
Get a motorbike rear shrunk down plate.  That'd look sweet!  It's illeagal but take it off if you get pulled for it!