And if mike doesn't sort something I will before summer. May need to borrow an 084 muffler to get dimensions from the back though. Id build a one piece billet milled ally from the back outwards with a flat front face plate with your opening custom sized, but looking as oem as possible. Probably have about 6 hours in the prototype but getting a batch cnc milled should bring the price down to oem ms880 prices or less.
The sky's the limit with this, it's just finding the god damn time to do it! And with that I feel mike probably has a better chance than me at present!