[snellemin]

The way I see it is this.

Big 2 pole and 4 pole motors will be maxed out at 50-60k rpm. So you pick your kv poison based on your available voltage. Keep the weight down and you will need less torque, which translates to less needed amperage. So a smaller/shorter motor can work.

Use thick wiring and good connectors. Keep the wires as short as possible, but enough to flex a bit.

Based off my experience in my smaller cars, I would say a 1515 is too small of a motor to turn those big tires at 60k motor rpm, for record breaking speeds. I would stay with a motor in the same diameter, but choose a longer can version like a 1518, or 1521 to gain the torque to turn a bigger gear.