How can i restore my 3Gs (old Bootrom) from 4.1 to 6.0.1

Hi everybody! I want to have my 3gs (now on 4.1, oldbootrom/jailbroken/ no unlock) to work on 6.0.1. i have the shsh blobs for that version, but the restore process always stucks on the latest version of redsnow. when i try to restore it stays in "waiting for device" screen and after 10 minutes the process fails and my phone reboots.. is there any other way to restore (on my mac)? pls help me!!