iPhone Keep unlock while upgrading jailbroken iphone from iOS 4.1 to 5.1?

[jonsn0w]

I have a jailbroken, unlocked 3GS running iOS 4.1. The baseband is 06.15.00, which I want to keep. I'd like to upgrade to iOS 5.1.1 without losing the untethered jailbreak and (non-carrier) unlock, assuming that's possible.

Would I be able to achieve this using redsn0w, or should I use something else?
Is it sufficient to have the SHSH blob listed in Cydia, or do I need to save them to the pc?
If I need to unlock in a separate procedure, what are the steps for that?

I've backed up my phone files, verified that I have 5.1.1 SHSH blob saved in Cydia, downloaded the appropriate 5.1.1 ipsw file from this list, and installed redsn0w.

I'm not sure which tutorial to follow from here...

 

[sbddude]

Use red snow to downgrade baseband to an unlockable one, then build a custom firmware to preserve that baseband

 

[darricksailo]

I believe you need to downgrade the baseband before updating the firmware

 

[jonsn0w]

Pardon the delayed response. I've finally had some time to read up on this and have more questions. Bear with me, I'm still learning. Am I on the right track?

1. Use redsn0w 0.9.15b2 to downgrade baseband to 5.13.04 (I plan to follow this tutorial)

-After completing baseband downgrade, how do I re-unlock and jailbreak? Does it matter which is done first?
-Do I need to look for a tutorial specifically for untethered jailbreak, or is there an option to choose untethered in redsn0w?
-I currently have ultrasn0w installed. Would that still be there after the bb downgrade?

Use red snow to downgrade baseband to an unlockable one, then build a custom firmware to preserve that baseband

Is that done by clicking Create Custom IPSW button in redsn0w, and then selecting the iPhone2,1_5.1.1_9B206_Restore.ipsw file? If not, could you clarify further?

Once the firmware is updated and the JB & unlock is done, do I use redsn0w again to get back to the 6.15.00 baseband - or does this need to be done in an earlier step?

Thanks in advance for your patience.

Additional phone info:
-new bootrom 359.3.2

 

[dhlizard]

You have to use older version of Redsn0w
The details are in the tutorial

http://m.iclarified.com/entry/index.php?enid=22652

 

[jonsn0w]

You have to use older version of Redsn0w
The details are in the tutorial

http://m.iclarified.com/entry/index.php?enid=22652

That's the same tutorial I linked in my post. Thanks anyway. I'm glad I got that part right, at least.

 

[dhlizard]

It works if you follow the instructions correctly.
You have to re-flash the iPad baseband
You have to use the older version of Redsn0w as the details in the tutorial show - the newer versions of Redsn0w will not work.
You run the downgrade procedure until it works.

Hundreds of thousands have successfully used this procedure to downgrade.