Lose A Few Volts

Hi All,
I'm using a 48v torroid transformer...67.2 VDC.
Using 3V 3A unipolar nema23 from Hobbycnc on Gecko G202's
Wired bipolar, series.
2.8 amps to the motors.

So far all is well, But i'd like to lose about 8 Volts.
Reason is the motors run at 150 degrees. I'd like to get
them down to around 130. I'm just more comfortable with them being
a little cooler. I'll drop the current down to around 2.2

Can i just put a few diodes on the transformer and lose the
8 or so volts? Is there a better way?

Thanks for the help,
John