I used TDB's windows flasher to change mine. Also, you said you wanted the region-free, but then weren't trying to use RPC1 version. Do you have a windows OS installed?
If you do a search on this forum, you will also find a f/w version modified by Liggy that does auto-bitsetting for +R media. That is the one I use(modified TDB's 2.23 if I remember correctly).
Were you able to successfully backup your firmware as suggested in the readme.txt?