I generally put failed C in RF if I think they can OPS .850 if I don't have a legit RF. I use 50ish PC all the time. Long ago, I found 10 pts in PC to be worth .12 runs in ERA. For the most part, it holds true. IOW, a 90 PC will be worth about half a run in ERA over a 50 PC. I'm not sure it's linear in that a 0 PC would cost a team just more than a run in ERA compared to a 100 PC but it works between 40-100.