iPhone 3GS on iOS4.0 upgrade to iOS5.1 questions

[00PS]

So I have a Jailbroken iPhone 3GS on iOS 4.0 and am having some issues with that have supposedly been fixed in newer versions. I'm thinking of upgrading to v5.1 but before I do I'm curious to know if I can downgrade, or revert, back to version 4.x. I have the SHSH saved for what seems like every version 4 revision (not for 5.x though).

Figured I'd ask before I did something I would regret.

 

[Jibs]

I haven't done a downgrade in a while, but the last time i did it wasn't that complicated. I've had this link bookmarked for a while and its what i used to do my downgrade in the past. http://www.iclarified.com/entry/index.php?enid=7557

When i upgraded my 3gs to 5.01 i was worried that i might want to go back. Since the upgrade i've found no reason to go back and i'm happy on 5.01.