So I did some modification to mine to get it to fit how I wanted...
Note: I don't mind at all modifying something like this, I do it all the time. The big reason I bought this diffuser over all the others is how it curves around the bumper and does a much better job completing the rear end.
This is the area I cut out:
Plenty of room now:
The diffuser is now completely flush up against the car, no spacers needed!!! YAY!
I also cut off about 1.5" from the two middle strakes, they were scrapping on my driveway

(The only place I've scraped with them so far too... oh well, still looks good)