Tom,
In steady winds, 10-20mph, I trim the main until the aft end of the boom is nearly over the inside of the inwale/deck and then trim the mizzen in until the tell tales stream aft. This will be quite a bit inboard in comparison to the main -- the mizzen boom is situated midway between the inner side deck and the c/l of the transom. In this configuration, I get consistent speeds to windward between 6 and 7 mph. She goes so nicely and with such little fuss that you hardly feel it, unless you are going into a good chop and getting a face full of spray. By the time the wind has hit 20, I have hardened the snotter up as much as it will go for it will be time to reef soon (if single handing I reef around 15; when I have crew I reef between 20-25). I have very little weather helm at this point, in fact, it is so slight that I would be tempted to call it neutral. I cannot say that even in winds up to 30mph (reefed of course), that I have had to wrestle the helm. This is the most pleasant boat, handling wise, that I have ever sailed.
In gusty conditions and during a gust, the boat wants to drive closer to the wind, if I am already sailing close hauled, all I need to do is make some slight adjustments on the tiller. Very little sail trim is necessary here. Fiddling with snotter tension during such flukey winds between light and gusty gets too exacting and finding a sprit tension that is not too loose and not too tight for the conditions is what I seek and then just leave it there.
In light winds up to 10 mph, I generally have the snotters eased to induce more draft and I do ease the main boom out over the side deck some and ease the mizzen to suit. Thinking about my local conditions (the inland lakes of Western Michigan and Lake Michigan), once the wind is under 10, it is rarely steady and very capricious. So I am always adjusting the tiller and the sails looking for the sweet spot. I can't say I have, as light air sailing is one of my greatest frustrations. In these kinds of conditions, I have neutral helm to lee helm. Trimming the mizzen in takes care of the lee helm. Some say you can get the cat-ketch to self steer, but I haven't found the magic for that for very long. Left over chop or boat wakes do not make it easy, in my estimation. The feeling of the helm does not change much from light to heavy winds and I sense no difference in the feeling of the helm on either tack.
NB: When reefed, I sail with the main in the third mast step. Helm balance is no different than with the two sail configuration in light to moderate winds. As I noted in another thread, I bet I could put the mizzen in the reefed position in winds above 30 and sail comfortably and confidently into the 40 mph range.