Tell your guy to get more familiar with halftone choices and LPI settings. Avoid those halftone types that automate LPI settings and offer no control such as GerberTone. For process fills start with Classical Dot for the halftone type and then either 53 or 70.7 for the LPI. For photos, choose GerberTone STC Photo and again, either 53 or 70.7 for the Lines Per Inch.
The LPI numbers are specifically chosen because they work well with the resolution of the Edge printhead. The lower the LPI number the better the tonal quality of the print will be but the halftone dots are larger and will be grainier than those set at 70.7 LPI. The higher the number the finer the halftone dot size but at the price of tonal quality. Each has its place and mostly depends on the anticipated viewing distance. High LPI at arm's length and lower LPI at five feet or more is a reasonable rule of thumb.
