Merion #5 is a beast for sure.
The pin placement on Oakmont #9 is the key, the pin behind the trap especially from the back tees is very tough, rarely make a birdie there and often 3 putt if I go long. If you play short in the trap or fairway you have a fairly easy par.
In terms of Merion #5, the middle/left pin is impossible, actually unfair in my opinion. I don't recall where the other pin is, probably back.