Don I'm far from an expert but on my 5.8 or A its really obvious when I need downhaul as the windward hull tends to fly high but the boat wont go fast forward. When your sailing if everytime a bit of a gust comes along your windward hull rears up and you need to dump main or steer into the wind dramatically, then you probably need more downhaul. If so far you've been comfortable in the conditions you sail in then just enjoy the boat.
regards