[OS X TeX] Changing TeXShop Matrix Panel size

[Kirk Lowery]

TeXShop's matrix panel defaults to 10x10 size. I use it to create
complex linguistic trees with xyling. Very handy.

According to the help file, one can change the size with the command:

$ defaults write TeXShop matrixsize 12

However, when I execute that command (with 12 or any other number),
restart TeXShop and bring up the matrix panel, nothing has happened.
The maximum matrix size is still 10x10.

What am I doing wrong?

Kirk