FWIW, I have Oldpinguys plastic and while it works well, it did not eliminate airballs 100%.
What had a major effect on the source of the airballs was increasing the forward tilt of the two targets. I did this by sandwiching a .020 piece of styrene shim stock between the target bracket and playfield. It is about 1/8" wide and rests on top of the screw shafts as they get tightened.
Super simple and effective.