Right now, I have an iPhone 4 with firmware 4.2.1 on AT&T. It is jailbroken with a version of greenpois0n. I also have tinyumbrella with SHSH blobs saved for all firmwares between 4.2.1 and 5.1. I was wondering if it was possible to do a custom upgrade from 4.2.1 to iOS 5.0.1. I didn't do this before, because I have GPSphone and I wasn't sure if it would be compatible with a jailbreak on iOS 5. Anyhow, Apple is not signing iOS 5.0.1 anymore, but I'd like to upgrade to that firmware for an untethered jailbreak. Is there any safe way to do this? And is it even worth the trouble? I've had some pretty scary moments jail breaking in my past lol.