The first thing I designed for this vehicle was the wheel.  Not only is it a spheroid design, but the tire is able to rotate freely while the sides stay locked in place.  This makes it possible for the two guns to stay parallel even though the front wheel is only attached on the left side, exactly as the real Batpod was designed.  This is the second major design that I came up with, as the original frame was far too chunky to look right.  I'd spent weeks trying to come up with a brick-built frame that was as small as possible, but it wasn't until after I actually watched The Dark Knight that I finally remembered how wonderful flex tube can be in the right situations.  In order to help it keep such a pronounced bow without either springing back open or kinking, I inserted a cut length of straightened paper-clip before flexing it into shape.  The resulting frame still isn't terribly accurate, but it's a lot better than the first design, and it's as close as I can get it with stock LEGO parts.  It also has the advantage of being able to drop flat to the ground, just in case there are any high-riding semi trailers around.  Or, uh, it can ride high, just in case there are any nearby cars that need crushing.