I have a TBM Silent beauty pitts and it cracked after ~1 gallon thru.
The prop is balanced and the hub is also.
Running the engine just so ever slightly on the rich side.
After the muffler cracked at a weld joint, I went back to the site to get phone number and seen the new updated bracket requirement.
I welded up and will continue to fly it, in the mean time going to make my own but a few oz's heavier.
Use similar design just thicker material and a little more volume.