I believe there's enough room to get in there with the right burr if you just bend the middle of the deflector up. But a quarter inch shaft burr about 4" long would be nice to reach back in there to open it up. But the problem is the added heat on your hand. If it didn't need to be stealthy, I always try and add 1 on the right hand side blowing forward because of that reasonAround here the fallers i've talked to about it will use any muffler they want except during the peak of fire season. If you want to keep it as stealthy as possible cut the stock deflector mostly off and fold it back. The stock opening can be opened about 3x as much. Then fold it back down and weld it back up. Or maybe braze it?