Well I for sure don't understand that. The position of the front hole in the rudder determines the rake. The tiller assembly pushes the top of the rudder back, bottom of the rudder goes forward, so that it touches the front of the lower rudder casting. What's adjustable? The little screw in the lower casting only adjusts how deep you want the hole punched in your rudder.
So assume that you didn't change your rudders. Do you have tiller pull? How much?
I'm not sure your level of experience. However, the last part of tuning is to adjust the rudders for helm feel. My point was...get the sail set the way you want it and then determine how much helm you have. It will most likely be weather helm, but you may be surprised that it isn't too much.
Drilling is a hit and miss proposal and it may not take much to get the feel you want. The adjustable arms make it so you don't have to drill, you can just make small changes as appropriate.
The adjustable upper arms have a bolt and plate that can be moved to adjust rudder rake. You can actually convert the non-adjustable arms to adjustable, but it takes some skill with a drill press and file.
