The only way to find out is get out there and do it, but i suggest
your biggest enemy will be sea state. It will be easier in flatter water.
And you must be preparred to sacrifice speed. Consider the schooner
going dead downwind (not that you'd ever want to). one sail either
side and both eased past amidships. This should self steer DDW til a
big wave comes along.
Of course wind abeam or forward it should be easy, and if the boat is
really fast your apparent could be kept on the beam even going
downwind. Can't wait to get one in the water and play with it.