that combo results in a 510mm lens (including DX crop). ....
I thought that lens focal length and DX crop were two different things. 200mm & 1.7tc = 340 focal length regerdless of camera and the "dx crop" simply meant that the field of view was narrower, which in the case of this photograph, reduces how much of the scene is visible to the right of the nose and to the left of the tail. The airplane would be the same size thru the lens of a film camera as it looks thru a dx camera.