It may be worth noting some 6950s cannot be unlocked because the flash is hardware locked so although one can easily make a proper rom one cannot flash it, for example XFX 6950s hardware revision A.3 (current Newegg offering) cannot be flashed. With that said techpowerup is one of the best sites to go for information and I have a thread going over there on a physical hardware hack, not sure if it will work yet but I'm playing with it.
I am in the same boat... I can push 350MH/s with overclocking but haven't been too stable at that level so I run just a bit of overclock and get ~330MH/s. Somehow I managed to randomly get a model that can't (yet) be unlocked. I read the thread you started and will follow it.