Trying to downgrade iPhone 4 on stock, non-jailbroken 5.1.1 to 5.0.1. I opened redsn0w 0.9.11b1, and chose "Stitch", browsed to the official 5.0.1 ipsw, and let redsn0w stitch my blobs from Cydia (I've also tried all of this using local shsh blobs, got the same error). I set my hosts file to 188.8.131.52 gs.apple.com, and used redsn0w to put the phone in pwned DFU mode. I the use iTunes to Restore, browsing to the newly created ipsw, and after the "Extracting Software" stage, I always get iTunes error 1600. Any idea what I'm doing wrong?