Some rules can't be overcome, but sometimes people don't care either
For what it is worth a rule that can be bent or even tossed out the window depending on what one considers acceptable would be the ratios and is one angle of experimentation that even a beginner straddled with an on camera flash can use to improve a shot with something as simple as a reflector.
Wayne -- If you cannot fix it with a buttset and some beanies you ain't a technician