What voltage power supply do you have?
The biggest reason for wiring an 8-wire motor in series is if your driver doesn't have the current to drive it in parallel. That driver can run up to 7A, and the motor only needs 6.1A in parallel, so sticking with parallel is probably your best bet. Also the torque charts on the automationtechnologies website show the motor being stronger across the range in parallel when run from 48v.