Unzip this into your baseq3 directory. Go into quark3 and change your effects color to white. It will not work otherwise. Then change these variables:
/r_railsegmentlength 20
/r_railwidth 40
/cg_railtrailtime 300
This should make your rail look like q2's rail. Feel free to tweak the variables to your liking.
To uninstall change the variables back to the old ones...the defaults can be found by simply typing the command with no variable number. Then delete the railfx.pk3.
