What is the bore size of that stainless insert? What you are going to find is that the tip of the insert will get peened by the high velocity plasma. That will cause the bore to close up somewhat. I that bore is too tight to begin with it could cause "bullet strikes" which totally destroy all accuracy.
FWIW a conical baffle is not nearly so efficient at stripping off high velocity has as you might think. It can only really affect the outside surface of the gas jet. Otherwise the gas jet tends to flow straight forward without being affected. That's the reason conical baffles are not used much in silencers these days.
Pete Lincoln, of Roedale, spent a hell of pile and money testing his brake design in more than one laboratory in Europe. He has sent hundreds of brakes, to happy customers like me, all over the world. Tens of thousands of rounds have been shot through his brakes. I have yet to read of one instance of a bullet strike due to your theory. A brake is not a silencer. While they share certain characteristics, they are not the same.
In short, to the OP, I would certainly be more inclined to seek out advice from those that actualy own and use the product as opposed to those that have not.
R.