All good, but still wondering about that 777 approach speed bump. Vmca is approximately 136-137 KIAS and so, so depending on flap settings you'll hit the floor at weights something below 460,000 pounds . But something else happens at the lighter weights that I cannot find. I show Vref go from 136 at 340,000 pounds to 143 at 339,000 pounds and below. I have yet to find a satisfactory explanation for this.