stepper drives and motor size

I got my new Warner drives today.I spent some time reading through the
instruction book. It has a caution: Do not use larger frame size motor
than those listed, or the drive may be damaged. If a larger frame size
motor must be used, consult the factory for recommendations.
Well, I made that phone call. The recommendation was for a different,
very expensive(over $2000) drive. The problem with the NEMA 42 motors,he
said, was a voltage increase in the buss when the motors are stopped
quickly as in a high friction situation,which I certainly
have(Bridgeport conversion).
These drives are rated at 75Vdc and7A. I will be using only 5A and
probably 56Vdc.
Anything that I can do to protect these drives while running NEMA 42
motors? Would microstep resolution make a difference as far as induced
voltage ? Anything that I can add to the cicuit to the motors for
protection?
Carey