Jock, of course we configure as per the Boeing performance figures, F20 always. I used the clean case to avoid bogging down in what is a huge number of combinations when you start considering FR, Rtg1 or Rtg2. Throw in overspeed and 2nd segment considerations and we can post for a month. BTW our tyres are rated to 235Kt so no problem
It is not possible to fly to Vmca because it is below Vs1g in almost all conceivable situations, that is my point. How Boeing derived those numbers and satisfied the airworthiness authorities has always made me wonder too. Actually Vmcg is the driver for light weight T/O in the B744 because of the factoring of V1. Like for like, Vmca is always less.