Well, this clears a whole bunch up for me. I'm on 11.0. I have the save installed correctly through my dongle. So now it's just try, try again?It's probably because, as far as I understand it, putting a payload on the SD doesn't actually do anything. Installing OoThax either via the homebrew application or by Powersaves installs the payload into the save file itself (whether it be on the card or a digital copy).
OoThax will boot fine on 9.0 - 10.7 without needing any extra payload on the SD, and on 11.0 it will boot very, very infrequently, and putting a payload on the SD will not help with this.
The only time when a payload.bin file on the SD card would come into the equation is if you wanted to use the OoThax installer homebrew to perform an offline installation, in which case you'd put payload.bin in the same folder as the homebrew application.