Going from 72v to 52v

So the scenario is, I got my hands on a beat up EM1 sans battery/charger. I have a few packs I can use, a 48v 36Ah Pack and a 52v 30Ah pack. The controller is programmable so I know that will be fine for either pack. The last part of the equation is the motor. I think I know the answer but all the writings here talk of running 72 volts through a 48v system. I think if my reading is correct feeding the 72v hub will only result in a decreased speed and torque, that being said many hub motors are advertised as 48-96v only the rpms drop with lower voltage. So my questions are 2 fold. Will the motor work with less voltage, I'm not looking to rock the world , 32 - 45km/hr will be okay for the moment? Will say a 48v motor rated around 1500 watt be any improvement. The controller Max's out at 50Amp so I don't see many issues other that the motor is incompatible with my plans so I'm looking for honest opinions, again the plan is a reliable speed with good torque. Is the motor useless for this plan, I have no issues selling the motor on and buying something that will work if this won't.

The biggest thing will be the lower top speed. You will have to test it and see if it goes fast enough for your needs. The power rating of the motor is not really changing, so you should still have decent acceleration with the right controller settings.