Here: elotrolado.net/viewtopic.php?f=179&t=1518203&p=1722815503#p172281 5503
The drowngrade failed to a this guy and the PS3 was bricked, here is the log:
The guy was scared cause his PS3 don't turn ON and no image.
"update package elapsed time = 181289 msec
Updating or Verifying failure 0x8002f057
manufacturing updating FAILURE(0x8002f057)
Total Elapsed time = 182526 msec"
He copied the 3.50 retail update and the LV1DIAG (don't know the exact name)and the PS3 started again to update, this time fine and now it has 3.50 again