The combo of pushing the limits on how low you can get your tire pressure and how fast you can get over obstacles is the perfect recipe for pinch flats. I've already gotten more flats this CX season than I did an entire year in road training/racing.
So I've forgone trying to attain the lowest possible pressure in the back. I'm rocking 40ish psi in the front, 45psi in the back; and for training 45 in the front, 50 in the back; and just riding 55 on both.
This day my teammate was the unlucky one, getting a flat on his custom steel Snyder bike, a local Atlanta bike builder.