This method basicaly uses linearTargeting, but instead of using the current enemy's velocity, you keep a log of all of its recorded velocities: and shooting at the "highest" point in the graph.
This sounds very similar to the aiming method that Stampede 1.3.3 currently uses (except it has both a linear and a circular version in a VG array). I have not been able to improve it much further than the gun currently in the RR; however that is probably due to my sloppy implementation rather than a weakness in the concept. I'm curious to see how you fare with this. --wcsv