First if you don’t have the exact car I have take the time to check your mount version (1 or 2). I got my hands on version 1 and I ended up needing Version 2…good thing the wife’s a3 could use the mount 
Unfortunately with the TTS (and I’m going to assume the TT) the belly pan must be dropped in order to access the insert.
It’s…quite a long belly pan, spanning half the car from bumper tip to the backs of the doors.
5 small black screws per side
1 large black screw front and center (has a yellow mark)
3 large silver bolts with washers towards the back (secured with Loc-tite blue)
There are 6 additional bolts at the very back but are not necessary to remove since you should be able to move the belly pan enough to get access to where you need work.
http://images.tapatalk-cdn.com/15/12/12/a8143d0d91048741d90abdf3871c915c.jpg
http://images.tapatalk-cdn.com/15/12/12/1f9b0356c080b5fe8ab4b3f6381d4d2d.jpg
http://images.tapatalk-cdn.com/15/12/12/2b74f172bfa6283f8aac4483c87ab361.jpg
Install the mount, trq to 100ftlbs and button back up!
-AZ