In an effort to reduce/eliminate the airballs off the left ramp on my pro I did the following. I remove the target assemblies and bent the mounting point of the bracket about 5 degrees. These brackets are tough so you may need 2 pairs of pliers. I used a vice grip to hold and pliers to bend. Make sure you bend it the right way too and don't over do it! About 5 degrees (roughly) is all you need. The difference is very noticeable now. Edge shots off the targets bounce slightly off the playfield instead of being ballistic moon shots. You cannot visible tell anything was done either because the angle change is slight.
Edit: It does not 100% eliminate airballs, but significantly reduces them. I was playing and trying to cause airballs by hitting the 2x and 3x targets. I did get a medium airball off the 2x once. Most other times the ball just bounced about 1/4 inch or less off the playfield.
These target brackets are really well designed and strong! The design even keeps them from fanning out sideways.