I have an iphone 3g unlocked and jailbroken at 3.1.2 and want to get it in the same unlocked state into 3.1.3 jailbroken. Do I have to make a custom baseband upgrade free 3.1.3 firmware? If so how do I go about doing it? Also is it worth the effort? I am willing to it as I am giving my iphone to a friend and don't want him upgrading it accidentally through itunes and me losing the unlock.