If you chose to climb at Vfto you would be a complete dillon. Vfto is min clean after slat retraction. Other than fourth segment following an engine failure I would never climb at Vfto and even in hat scenario I would probably climb at a higher speed unless I was gradient limited - what would be the point? I doubt 300/M0.8 best rate either - thats almost certainly a cruise climb or high speed climb schedule and nothing to do with Vy. I commonly use 300/M0.8 or 0.82 but if I was trying to climb more quickly i may slow to 250 and use 78 on conversion but the calculations are not easy as it involves he mass of the aircraft, ISA, and the amount of power you get changes a bit with airspeed. So the last time I needed to get to FL450 in a hurry, which was for a NAT entry point out of Goose, I requested an orbit rather than fanny about trying to zoom climb just to get up more quickly. If you try to get too high a climb rate and the airspeed is reducing, the ITT rises and you arent doing the engines any good and I dont really want to cane a few million dollars worth of engines simply to reduce the track miles to an altitude.