Since the singing window for 4.3.5 is now closed, this guide is no longer valid. If you didn't manage to get it to work before approx 20:00 on 17/10 then you are out of luck. The process simply won't work now. You cannot downgrade a baseband once Apple has stopped providing the firmware signature for it.
To avoid any unnecessary bumping of the thread, it is now closed from further posts.