ps3 jailbreak DG ing

the site i found this on said that this was all that was needed to downgrade 3.55 plus to 4.25 it also stated the file should be renamed PS3UPDAT.PUP could someone let me know if this works there where no survey or password in getting this don't want anyone to brick so only attempt if you have flasher/reader please respond want to know if it is true this is the only one ive found ive been digging for days