Rudder: Opening up the starboard side

The big question....where to cut into the rudder. I used a drill to figure out where the balsa ends on the leading and trailing edges of the rudder. The marker lines indicate that below the water line I need to cut:

- 3.5 inches from the trailing edge
- 1 inch from the leading edge

Above the water line I can cut a close as 1 inch on both sides.

I'm using a grinder with a metal cutting disc to do the job.
The first section is open!

The second section...on the starboard side.
As you can see I was close, the cut can be no closer than 3.25 inches from the below waterline trailing edge.