My D9200 has a flat section right under the front of the tube and the angled section in back.  I don't have a protractor handy, but if I remember my trigonometry correctly, that angled section is approximately 13 degrees tilted.  Don't design a cabinet based on this - somebody's got to have a more accurate measurement - mine's already in the cabinet.
That being said, I secured a 2x4 for the top and bottom mounting brackets of the D9200 (above and below the screen).  I put both 2x4's 4-1/2" back from the front edge of the cabinet sides.  That way, the angle of the cabinet is what dictates the screen angle.  This is the way I believe these screens are supposed to be mounted.