GDFS can be flashed with FAR and using DCU-60 but, as luzer said, you may brick your phone.
I'll try to post the GDFS address soon.
Found GDFS addresses only for k750/w800/k700/z800. Sorry, but no luck for w810:(. You can find more info abou GDFS writing right here on http://www.topsony.com/forum/showthread.php?t=26