Good tips above. I will add that a straight wing leading edge (like an Edge) typically fares better in harriers than swept leading edges. I don't like the looks of Edges, but I have flown a couple, and they definitely exceled in harrier flight, and I loved how they flew 3D. I think SFG's (side force generators) also help some.

Be sure to override the tendency to steer a little with ailerons while in harrier. I am bad about that and frequently fight wing-rock. Try to use ailerons only to keep the wings level, and steer only with the rudder.