I've seen a lot about not being able to downgrade back from iOS 6.1.3 for iPhone 4S & 5. People said it was possible to do so with an A4 device (iPhone 4) as it's possible to save the SHSH blobs or whatever they are called. I just tried to save mine with TinyUmbrella and it told me Apple is no longer signing that. What gives? How can I save mine so that I can get back to 6.1.2 if anything goes wrong?