This was our upgrade procedure as well (126.96.36.199 to 188.8.131.52). Prior to performing the upgrade we test the roll back in a test environment.
The roll back procedure is very easy. Just make sure you have a clean backup of your 2.2 BES folder.
If the upgrade were to fail you could uninstall BES 4.1 and re-install 2.2 and replace the BES folder. It is very easy.
Oh did i mention, Make Sure You Have a Backup of Your 2.2 Folder!