Great news has just come from MuscleNerd. He says that updated RedSn0w 0.9.11b1 was released by iPhone Dev Team specially for A5 (A5X) devices(iPad 2, iPad 3 and iPhone 4S).
A couple of days ago I
wrote that updated of RedSn0w can downgrade iOS 5.1.1 to lower version of iOS for untethered jailbreak. Today this day have come.
Latest tweets from MuscleNerd
account on Twitter shows some tips how to perform iOS downgrade on iPhone 4S, iPad 2, iPad 3.
Look at what he said:

As you see that all you need is to download RedSn0w 0.9.11b1 and perform iOS 5.1.1 downgrade on A5 and A5X devices going to
Extras => Even More => Restore.
But because of "
accidentally" leaving out of .plist file you need to pointing RedSn0w at the
9A405 version of iOS 5.0.1 version on iPhone 4S during the downgrading process.
Update: New RedSn0w 0.9.11b2 can fix that problem.
Here is download links and tips.
So here are direct links below which you can use to download RedSn0w 0.9.11b1.
Download RedSn0w
RedSn0w 0.9.11b1 for
Windows users.
RedSn0w 0.9.11b1 for
Mac users.
Note: If you are Windows user then don't forget to Run the tool as Administrator.
But if you want to start making iOS 5.1.1 downgrade then first listen to me.You need to back up SHSH blobs of the iOS firmware to which you want to downgrade to. You may want to downgrade new iOS 5.1.1 on A5 (A5X) devices because there is no untethered jailbreak for new iOS yet.
To back up SHSH blobs is essential thing for downgrade. If you are downgrading your iOS to lower firmware you have to supply Apple with SHSH blobs of the lower version for certification. If all goes correct and Apple servers take
shsh files and approve them you'll be able to use iOS firmware you want.
Without
SHSH blobs saved you can’t to perform downgrade. That’s why it is important to save them.
The detailed tutorial guide on how to perform iOS 5.1.1 downgrade on A5 (A5X) devices will come soon. Stay tuned with us and you will see it. Also you can leave your suggestions in the comment version below.
Update: Here is the
tutorial guide which you can use to downgrade iOS 5.1.1 using RedSn0w 1.9.11b1.