PS3 break team finally solve the downgrade problem, congratulations to them!
this is the quote from official site:"
Hot news: All series of PS3BREAK dongles support downgrade 3.5 perfectly
PS3BREAK team release the latest PS3 break downgrade mode firmware. Referring to reasons unexpected, delay to release these for this time. Sorry for the inconvenience caused. "
All of the PS3 break from them are availble for downgrading now.
PS3 break official seller
PS3 break news
PS3 break downgrade