legit sauce? (4.20 to 3.55 d.g)

hi i have a pS3 on that there 3.72 (CECHG03) and want to "jailbreak/hack/mod/make love to" it.


I've done a bit of googling and come up with the outcome "no. need to hardware flash the mofo" so i cant do anything without performing some type of surgery on the ps3 unit itself, cutting, chopping, soldering.... (scary thought)

now! most of the places ive read seem to be a few years old and so id like to know what other options are available if any!!

and ive seen this: "PS3 4.20 Downgrade to 3.55"

" Notice:Downgrade if you already updated to 4.20 use this Downgrade! You must be on OFW 4.20 if not then FW update.
You DON’T need Flasher (E3 flasher, progskeet) You need only USB Stick with minimum capacity 256mb.

Instructions:

STEP 1: Plug a USB stick into your computer
STEP 2: Create a folder in the root of the USB stick called PS3
STEP 3: Create a folder inside the PS3 folder called UPDATE
STEP 4: Download PS3 PUP Updated
STEP 5: Unzip PS3UPDAT.PUP
STEP 6: Move PS3UPDAT.PUP to the directory UPDATE that you just created on the USB stick
STEP 7: Plug the USB stick into your PS3
STEP 8: Navigate to Settings Tab
STEP 9: Choose System Update
STEP 10: Choose Update via Storage Media
STEP 11: It will say it found Version 4.20-Downgrade-3.55
STEP 12: Choose OK
STEP 13: Accept Conditions and Install Update
STEP 14: After less than a minute, your PS3 will update, beep 4 times then shut down.
STEP 15: Power up your PS3 (You will have to do it on the console and not by the controller)
STEP 16: Your PS3 is now on 3.55!

Work on All models slim and fat.
100% tested works!
"

im not sure if im allowed to post weblinks so im saying sorry in advance if its not cool:
*link removed*

let me know if its legit brosephs, and if not... whats my options.

thanks for your time and help!