Idea: instead of using one shockwave pof, use 2.
A first pof thats not as thick with ends that meet at the trailing edge, essentially a flatter more disc like pof, mapped with a shockwave animation as seen from above. Render this first.
A second pof like the current one, mapped from the front with a animation thats mostly white, rendered semitranslucent just ahead of the first pof. In effect, you'd get a blast wave look ahead of the main wave.
If you could apply alpha blending to the rendering of the maps for the pofs, this would be even better and you could leave the second pof almost fully opaque (since the fading to black on the map would handle the transition).
Opinions?