I just use black ABS cement. Very similar to PVC, but its just for ABS, and its basically ABS plastic in Acetone.
Good as new when dry.
Ive put tabs back on the fairing with it, and was surprised to see how well they held...actually dropped one, and it didnt break off when the repaired tab hit the floor...and no, it wasnt dropped purposely.
Id think for a larger repair, something easier should be used because its hard to hold something in position for the time it takes it to start to harden up. But for those, Ill take a hot soldering iron to the pieces first to hold them.