You can turn down the flash if you like.

I've tried to find out the meter-candle-seconds of my EG&G but here on APUG, we haven't concluded exactly what I've got. So I don't know the math. In my case I believe that the No. 96 ND filter is a little "yellow" so "sensitometrically" I am getting more density than I calculated. Especially in blue light which film is most sensitive.

This is why I recommend a physical neutral filter. IC-Racer can show you pictures of what I mean, he has cut some out of acrylic.

But you don't need the accuracy of illumination to get results that are good enough for process control testing.

The goal is easy: You want to expose enough but not too much. You want to reduce the light output to the point that the graph drops down near zero (above B+F) in the toe. In case you cannot reduce the light that much, it's OK if your lowest toe reading falls around 0.10 (above B+F).

To repeat my earlier post, if the flashmeter indicates f/1.0 at ISO 100 - you are pretty close to what you need.