Thanx for all the quick responses out there.

First of all, most of the suggestions will not apply, because simply the construction will not allow it.
I've attached a few pictures so you'll see. I will try the loc-tite stuff and wait for better weather to give it a try.
Strange that I didn't overcome this problem with my other muffler, only that one was made from Stainless Steel.
Maybe it has something to do with material and expansion with it.
By the way how hot will the muffler be at a regular aerobatic flight? And does it matter if I inject smoke, because I inject diesel.

Greetz

Thierry