Though steady-state the current limit will be about 40A, for short bursts you can go well above that. Probably not super helpful as you already showed this isn’t the limiting factor.
At a certain point, even with enough traction, your center of mass location becomes a limiting factor. With enough acceleration you start to pop wheelies and eventually flip.
Finally, if you design things solid enough and don’t mind scaring the daylights out of the opposing alliance, the robot doesn’t have to hit zero velocity prior to traveling the full length of the field.
At first using the encoders, then comparing the theoretical times for a 20 ft dash to the actual ones and seeing that those match, to account for slipping.
4 775’s per side seem to do the trick
Because of our teams budget last year we used the KOP drive again. We made the Ontario provincial championships. The drive-train speed is around 10-11 ft/s with cims and standard gearing. We found this speed was not ideal because it could not push other robots. If a defense robot blocked one tower we would drive to the other tower and often their drive-train speed was the same for faster and we could not reach the other tower before them. A drive-train at 12-14 ft/s will do much better. Too fast it may become hard to control, the limit I remember seeing is around 20 ft/s. Shifting comes down to budget and often better mechanisms should be priority. Also you may want to consider getting brush-less motors for your drive-train instead of shifting.