I did the additional interior carbon, as per the OP. It really lifts the interior. I did the shifter, surround and handbrake first which looked great, but the lack of steering wheel carbon started to bug me, so I bit the bullet and did that too. I have the black grills and gills, MPE and carbon diffuser, but I'm trying to resist any further exterior carbon...wish me luck!
The dental floss trick on the DCT shifter insert is definitely the way to go, just go steady and it comes off cleanly to the point that it's reusable, should the replacement ever get scuffed.