PSP has all 4 factory Corvette protectors. I know this, because my prototype game was manufactured without any, and I had to add them as within a couple hundred plays, the LT5 ramp was cracking.
All good. James from Pinball Inc had a surplus of protectors and threw them in with the other Pinball Inc Ramp that was received during the week
The next Corvette I do will have exactly the same setup. Pinball Inc LT-5 Ramp with factory protectors.