I'm not sure what kind of lamp housing you are using with your soft box. Solutions: lamp with smaller (less wattage) lamp(s); add wire scrims in front of the bulb housing if possible; add ND sheets to the front of the unit.
The easiest would be to use a different lamp. I wouldn't use the "real" Starlite globe. If I recall they are 500w or 1000w clear glass bare bulbs. I believe they have a regular Edison screw-in base so it would be super easy to put a lower-wattage tungsten or CFL lamp in it.
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