I've had a similar issue with different pipes. Mine are Rinehart True Duals and the rear pipe comes out and has a bracket that mounts to the near the top of the starter. It is much smaller than yours but it has broke in two pieces before. I attribute it to not fitting the exhaust up on the bike LOOSE first and then work front to back tightening everything. This way your less likely to put a bind on it for the torque to finish the job.
Welcome to the forum!
I have seen this tip several times and just instinctively adjusted exhaust systems this way on any vehicle type with great results. When it comes to working on Harley's Bodeen, Tourbox, Jack, and Bubbie (not necessarily in this order) are like E. F. Hutton, when they speak everyone should listen.