I looked up the RFW Injection for PS3 which promises a downgrade to the new CECH300X SKU's. I found the following information on an Indonesian website. Used google translate and cleaned up a bit to make it more sensible.
There is a gap between those who can not afford downgrade services / cannot downgrade their PS3 Slims CECH300x. That is because they use a method that is still vigorous and the hardware flashers Progskeet & E3 can not decrypt the protection system in IC NOR. Spansion NOR IC S29GL128P90TFIR2 used by Sony that Spansion, Samsung, and Macronix. For the type of memory that is 1x16MB Flah NOR (Spansion S29GL128P90TFIR2, Samsung K8P2716UZC-QI4D or Macronix MX29GL128ELT2I-90G), IC output features the command "factory protection" so that any action at this address FW change which is smaller than syscon value (FW <syscon value) will result in the system "BRICK".
So basically, this is, metldr2.
This is what the RFW Injection claims to do..
There is a system that can change the value of the 3.55 syscon into the reconstruction FW, which we call RFW (Reconstructed Firmware). This is what we release, the "RFW Injection". With this method the PS3 with CECH 300x series can play pirated games/CFW 3.55.
Info: PS3 Slim 300x RFW (Reconstructed Firmware) will be released on November 2012. RFW system with CFW means NO PSN ACCESS FOREVER, can play HDD games, install .pkg/other applications, and also supports the OtherOS feature (you can install any OS on the PS3).
RFW Version:The CFW used is Rogero CFW v3.x based with some modifications. DO NOT CHANGE THE SYSTEM FIRMWARE, except for install package files(.Pkg). A CFW for True Blue Dongle JB2 and JB-King Will be Released.
So, this gives us a pretty good idea of what they are saying. Now, can anyone confirm if this is legit??
Source : http://www.m.kaskus.com/showthread.php?t=16045839