I haven't test fitted it to a HR to be honest so couldn't say, is there any difference except the hole? 
 
  
Yes unfortunately. I got a flat one off fleabay that was flat. I had to enlarge the cut out on the right and build up the back with 3 layers of double sided tape. It didn't last so i took it off, although it does deflect the air. 
It's not flat underneath and has dips in the moulding. 
A flat one just does not sit on it without a lot of work and swearing. 
I think R-T measured up for some HR carbon ones as he did a thread using my car. 
It died a death for somereason. 
If you search through R-T threads it will show you what I mean. 
I will have a look as well and put a link up if I can find it!