i'm not a tornado sailor, but i have found the downhaul or cunningham to be a critical first adjustment to keep a catamaran in trim while racing. if the windward hull is popping or flying too high, you're just not making best speed... feathering up or travelling down are grosser adjustments that rob you of that fast-forward mode, in my experience. as crew, i give a touch of cunningham to help the skipper maintain heading, and it helps both of us if i'm not sawing through two feet of mainsheet every puff. once we've hit the bottom of the cunningham setting, it is time to wind up the diamond wires between races.
sam, how are you easing cunningham and main at the same time? i use both hands on the main, snatch a quick pull or ease on cunningham as needed, and right back to main trim.