If dead-downwind is feasible, wind direction is steady and not too variable, I typically raise the main to one side and fully extend the Genoa clew off the opposite side with a whisker pole - wing-and-wing. With auto-pilot, I do this even when solo-sailing.
You should find this arrangement to provide the maximum thrust without the otherwise negative effects of the main blanketing the head-sail, or solo difficulties of flying a spinnaker.
True Blue . . .
sold the Nauticat