Terminology question.....
When you refer to the "notch" are you referring to the notch in the end of the tiller arm, or are you referring to a keyway in the
rudder shaft bore of the tiller arm?
As Jim Cate mentions, you need a key & keyway cut into the rudder shaft and tiller arm to have an adequate mechanical link between the two
parts when operating under conditions of high load. So, better to relocate the cylinder around the existing keyway position, or have a new keyway cut into the tiller arm so that it centers the arm.