On my ketch the main doesn't extend aft of the dodger so it can't hit anyone unless they are out of the cockpit forward. Secondly, I seldom use the main and almost never use it down wind - I prefer to sail jib and jigger downwind sine I don't have to worry about shading my much bigger genoa with the small main or fool with sailing wing on wing. You do have to watch out for big gusts from astern when sailing downwind jib and jigger though. A really big gust can round the boat up since it hits the mizzen first