Just so that i am clear(been away from all of this a while)....others might have the same Question.This guide will only support you upgrading to a version of IOS which Apple is currently signing. At the time of writing, there is no known way to get around Apples security regardless of what SHSH Blobs you may have saved, so only the "current" version of IOS can be upgraded to.
Also did a few searches....mostly A4 responses.
I have an iPad 2 3G on 5.0.1 and i want to upgrade my jailbreak to 6.1.2.
I do have 6.1.2 SHSH blobs saved via TU. Is there any way to upgrade?
TU can't trick with the signing? or is this only for A4 devices?
Can the blobs be stitched into the firmware?
I feel noobish with these questions.