Hi Peter - The drive is current limited so if you connected two motors to one driver you would not cook it. I have done this on a couple of drivers to test (as cheap cncs do this) but the driver then gets weird feedback and you will either have midrange resonance or no high speed. You will need a 4 axis driver or 4 separate drivers.... I have run N17 motors on 1:5 reduction gearboxes and found that ratio to be a good spot for speed and torque. If your application needs fast rapids I'd go 1:3...Peter