Roger,

I have the IMF mainsail and the old-style blade centerboard.

I, too, was thinking about that relatively large moment arm of the rudder blade. The resulting leverage would magnify slight changes at the rudder, which, in combination with the relatively flat bottom of the R-22 hull, would make the force applied at the rudder all the more effective (if there were more of a keel, slight changes in the rudder would have much less an overall effect).

On a related note:
I also sail a Laser (which has a very flat bottom). A few years ago I discovered that I can steer the Laser with the daggerboard. I lock the tiller in a central position and ease the daggerboard up to fall off, down to head up. A change of an inch or so in depth is enough to change the heading a few degrees. This works best when sailing anywhere from a tight reach to a hard beat.

I spent a good amount of time this past season working to balance the R-22 helm with sail adjustments. Next season I'm going to start balancing helm with the rudder up-haul. I've never been so anxious for the season to start (I'll also learn if I put my centerboard back together properly).

Chris