I was pleasantly surprised to find that my custom ringtones survived the update! Although the songs do not appear in 'Sounds', they are still 'on' the iPhone.
As long as I don't update a contact, maybe the ringtones will stay??
p.s. I had used iToner to initially install them. and will not be editing any contacts with custom ringtones.
p.s. I had used iToner to initially install them. and will not be editing any contacts with custom ringtones.