umm, i'm just not mounting one at all, and leaving the plate in the window  
  
lol, how legal is that? 
  
I have been driving round with mine in the window for a while, as long as it is on show you should be fine for a while.  I am having some 'L' brackets in the mouth of the V3 using the number plate double side sticky strips.  Having a smaller than legal plate but not stupidly small as to get attention from the fuzz.  It will have to be one p'd off copper to pull me for it!!