I mounted huge 270 watt panels and did a video at hwy speeds (60+mph) which showed zero lifting of the panels from the roof (and they are not fastened down in the middle part of the roof so could lift if the airflow was actually causing lift.
This makes me think an air diverter/dam on the leading edge may not be necessary for panel mounting...depending of course how close you mount them to the roof.
I would think my flat roof would have more potential for lifting airflow than some of the traditional truck camper roofs with their protrusions.