I know I have a bad habit of posting hypothesis about what I can do or something I should do to help playing, but here goes. Today I believe I noticed that my range is cut off because I'm using too much of a tounge arch. I think I'm using it so much to where it just cuts off my throat and air when I get to certain higher notes. This may also explain the neck tension (trying to force through this small gap by too much of an arch), and how it is difficult to "blow through" my higher notes. I also notice this when I whistle were if I go to my extreme range it will eventually cut off most or all of the air from arching my tounge. Any thoughts?