I never opted to take any courses in aerodynamics, unfortunately, but my understanding is that establishing a laminar flow ( http://en.wikipedia.org/wiki/Laminar_flow ) is vital at those kinds of speeds, which requires a surface that the air can flow along smoothly. With a biggest-in-front arrangement, you get some slipstream benefit, but you also get a whole mess of turbulence, and there's no way you're going to rival the speed of a bullet train without a lot more energy spent. You want a mostly smooth/unbroken surface that the air can flow along.