I do not recommend to try it without a flasher installed and a dump of the flash.
To quote, roughly translated: Hi all, What better than to come back with this kind of news! Our friend and SGK developer releases today the result of hard work. Indeed, in the shadow he worked to bring us a CFW with features interesting and not yet seen the new CFW 4.xx
The basis of this CFW is based on Rogero 4.30 and the 4.21 Rebug CFW which is the most stable and most successful of the moment. He added SGKXMBM + Package Manager for our greatest pleasure. Some files from firmware 4.31 which ensures compatibility for the latest keysets. So you can play your backups favorites without a patch or fix. 4.31 is a spoof includes access to PSN and avoid unintended updates.
Added package SGKXMBM +
Lv1 Lv2 and recompiled.
Patched Peek & POKE
Coldboot game replaced
Theme changed from dynamic watch dogs
Testers and developers: consolehackdev / ZZ / dedalo! Teamsgk/ps3devs; SGK_84
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I updated to SGK 4.40.4 last night. All seemed well, I went into the Homebrew thingy and did the SGK FW update, it recognized everything and installed with success, it then asked to do a "Soft or Hard" reboot but gave no real explanation of the difference or WHY there was even a choice, it should automatically be the safest option.
I hit Yes, and seconds later, the system crashed and the screen saying something about the system being messed up and its going to reinstall the firmware and auto reboot. That scared the crap out of me and it seemed to go well until the reboot left me with a Blue Screen, no writing just a TV all blue (well boxed blue, as the res is 480i by default).