I own two. A 7* that I bought from Dr.G, last year, and a 5* that I bought new, a few weeks back. The newer one has slightly uneven width rails, but both play nice and sound the way I want them to. I've given thought to trying to even up the curved undercut of the sidewalls with a rattail file, but I'm not too confidant about the clearance, further into the chamber. I finally decided to not mess with a good thing. I really don't think the "air" can tell that there's a little more material to the left side of the window, than there is to the right side.