My question to Joe B: Have you tried the Lefreque sound bridge on a flute?
I have tried every contraption under the sun...personally. I have experimented with my own created gadgets...personally. And I can explain what the cause of just about any and all changes and even why it seems to affect some people and not others.
There are certain similar effects which are manifested by a variety of different "gadgets" that come in many shapes, forms, and styles, but they are all based on the same related principle and NOT what any of the market materials or explanations are that are touted with each device...
They all eventually fall into oblivion (always have). This is just another variation on the same theme. Give it time and it will disappear just like all the others..
There is no substitute for picking a flute suited to you and then going home and practicing. THAT, is the only thing that improves your playing and your sound...particularly the latter.
But if you've got a lot of money to throw away, go right ahead. And if you really, really need that "crutch," you can make your own for dirt cheap. Or you can just go practice.