I followed the same steps. Mine did open on vbe7. Then I edited the voltage, core clocks and fan control on vbe7, saved it to a new file name then flash it. Card accepted it. Editing in vbe7 corrected the checksum.
Hrmm.... not sure what I could have done wrong.. Guess will try again.
NEvermind, I'm an idiot, I thought vbe7 didn't open it, and was still showing the previous cards bios I opened but it did actually load it, and once I saved it with vbe7 it corrected the checksum. The part about using vbe7 is not present in the tutorial though. Should be added.