Why would the flash be sticking around long enough for you to be able to see the ship move past it? A passable-looking flash would be around for, like, a tenth of a second, tops. Basically one frame. If you're going fast enough to pass a single- or double-frame flash, you seriously need to un**** your table settings, because that's just plain wrong.
Anyway, I dunno about it working so well as a bitmap sprite or anything- it'd have to get seen from a lot of different angles, including from the front. Some simple, semitransparent, universal mesh would do nicely. Something vaguely like the subspace setup- just a basic cone (facing the other way of course) with a very short animated texture of about two frames, that activates whenever a flash-enabled weapon is fired.