[Bennett548]

You can get slightly faster times if the gear ratio is not constant. A linkage or, non-round pulley or sprocket set can accomplish this.

Do you account for voltage drop? Stalling all those motors drops the voltage considerably.

Do you consider the inertia of the motors? With the gear reduction, they end up making a significant contribution to the inertia of the system.

This is a good first step. Simulations should always start simply, and add other factors and complexity as you prove it out.