This fits the T-Mobile TM-AC1900 just fine!
For those (like me) who are concerned about removing antennas to access the back, the antenna connections allow you to rotate the chassis away from the wall a bit to make it easier to plug things in without everything falling out. Snap the bottom back in after cable work.
Before I found this, I was considering making my own (didn't know the T-mobile unit is basically a AC68U)... your design is much better than what mine would have been. Thanks!