That's where I read it. The DSS on-line manual, and a few other places. However, there is contradiction among authors here and there -
Jim Solomons Cookbook.
I will create a new set of flats for the next batch of lights - the results even at ISO 800 are a big improvement on dark calibration alone. It will take a day to calibrate, register and integrate that lot again - maybe down the track a bit.