I am trying to downgrade from 4.2.10 to 4.2.8. I have SHSH blob saved for 4.2.8 and it is recognized by TU. I have saved the 4.2.8 restore ipsw.

So I put my phone into DFU mode (blank screen), start TSS server in TU, go to iTunes and option/restore - select the 4.2.8 ipsw and it says it is restoring to 4.2.8. I run the restore and the software installs but when the firmware install begins I get a 1013 error. I kick out of DFU mode, see the apple for a second then it goes into restore mode. I then have to restore back to 4.2.10 (after commenting out the host files added by TU). I have looked all over the internet but cannot find a solution to this. I have noticed that when I restore to 2.4.10 it restores with an upgrade each time, so I think it recognizes the 2.4.8 firmware. Can I JB with my phone possibly on 2.4.8 in the state of a failed downgrade in restore or DFU?

I am on a Macbook Pro running Lion. I am frustrated but my phone is safely running 4.2.10. I am thinking I may have to do a tethered JB with redsn0w. Any thoughts would be appreciated. Thank you.