Fitted with SH34, and UK plate. Lots of room, but recently hit an unusually large pot-hole and snapped the plate in half.

Ignore the dirt and unfinished paint job.

You need to bend the number plate back at an angle, then it will bend rather than break if you hit a pothole. I've got the standard TC rack fitted on my TC Max.

When i had my bike i experienced the same issue, with the box fitted. I fixed it by attaching the number plate to the plastic mount of the box. Worked well but it does mean that the plate light is lighting up nothing. 

When i get my bike back i was gonna look at just getting a smaller plate to go in the default position.