Every other form where printers are attached in Apex has the ability to set the number of copies except for the Scale form. In my opinion this is a defect\oversight and needs corrected.
When using multiple scales one may use ScaleWatcher and the other not, there is no way to do this correctly when the system is set to print by scale.
Wayne, this isn't exactly what you are asking for, but today you could do this by:
Using a NULL printer (so that the ScaleWatcher print job goes nowhere)
Using a different printer so that you can specify a different .rpt file in Document setup, modifying that .rpt file so that it pulls 0 records (in records selection put something like 1=2), and in report options check to suppress printing if no records.