Yes thats it's regards bearings and rails thou you don't need to have the motor going up & down with the Z axis if you don't want.!
So long as your motor can handle the heavier weight then it will work ok but it can be done so the motor and screw stays on the Backplate reducing the amount of weight the motor as to move.
Does mean the back plate has to be the same or just longer length than the screw with a plate at the top for the motor to mount to. Depending on length Could also mean notching the front plate at the top to miss the motor/plate.? but like I say this depends on front plate length but if does need it then it's at the top which you don't use and will be minor and of very little detriment strength wise.!