I would invest in the pitch stop brace as well if you are doing the pitch stop mount, as I am unaware of anything being done to fix this problem. The mount is not what is failing, it is the brace that holds the mount. Therefore just replacing the mount with a stronger aftermarket one wont really help with the possibility of a broken brace. I would order the pitch stop brace from Perrin. I think they are the only ones that make one right now. Not sure though.
Pitch Stop Brace for 2015-17 WRX/STI
Pitch Stop Brace for 2015-17 WRX/STI