Hehe guys. I know how to restore a 5.1.1 backup on a 5.0.1 iPhone
hopefully this will make things easier for you guys, but you will need a 5.0.1 backup already in order to do this
When you get to the "restore from backup" page after downgrading, first choose the 5.0.1 backup. Then, iTunes will tell you that there is a newer backup (your 5.1.1/5.1 backups), and just select use newer backup. Normally if you select the 5.1.1 backup at first, iTunes will prompt you how the backup is a newer iOS version, blah blah. But if you use my method itll just skip that message and go straight to restoring
I was able to get all my text messages, apps, everything on my downgraded 5.0.1 iPhone from my 5.1.1 backup. Even the app layout and settings configurations were still the same