If you are adjusting your helm through rudder rake - that's all you are adjusting - the helm (the amount of pressure on the tiller). You are not changing the pressure the rudders need to keep the boat straight - although it does feel like it. When you change the rudder rake, you are only moving the center of effort (the centered location of the force generated by the rudders) closer or further away from the axis of rotation (the pintles).
Since some people reading this forum are new to sailing, or at least new to cat sailing, I think it bears stating that the primary way to adjust helm pressure is by the position of the traveler car. Many newer sailors leave the car centered or close to it most of the time, even when off the wind. They then 'trim' the sails by the mainsheet tension only, sheeting out farther when off the wind. This creates heavy windward helm due to a big mismatch in the Cl and Clr. You can't really adjust the Clr but you can adjust the Cl with the mainsail. The solution is to ease the traveler out and sheet in the main. Of course you want a little wind helm, but any more that a little and the boat is fighting the rudders and going slower.
Jimbo
