Toe in refers to the leading edge being closer than the trailing edge. If you think about it this way it may make sense. A catamaran slips sideways to leeward while sailing. You are using the rudder that is deepest in the water (leeward) to steer. The other rudder you want to disturb the water as little as possible. If that rudder (windward) were pointed exactly the amount that you would be sideslipping then it would not disturb the water much. On a daggerless boat (Prindle 16 or Hobie 16) you can use 1/8 to 1/4 inches for your toe in when the rudders are in sailing position (down).

Too much Weather Helm can be taken care of one of two ways either the rudders can tucked under the boat (forward) more or the mast can be moved forward. On a daggerless boat you are using your rudder for two purposes it doubles as a daggerboard as well. For that you would like to get the center of effort of the sail over the rudder by moving it back. This will load up the rudders helm so to counteract that you move the rudders forward. You can measure from the center of the rudder pin down the forward edge of the rudder at the maximum point will be about 1 1/8 inches forward of that line.

Hope this helps,
Dan