Moom has two different grids available during use. The first is the Mouse grid, which is set when you enable the full screen (or hexagon) grid in Moom's Mouse settings. The second is the grid used when defining custom controls; you set that grid size at the bottom of the Custom tab of Moom's settings.

Regardless of which grid type you're setting, the maximum value is 25. But if you've got an ultra-large display, you may want more than 25 sections in your grid. Through a hidden setting, you can greatly increase the grid size limit. Quit Moom, open Terminal, and paste the following line:

defaults write com.manytricks.Moom "Grid: Maximum Dimension Size" -int 60

Replace 60 with the maximum size you'd like to use, then relaunch Moom. You'll find you can now type a number up to 60 (or whatever value you used) in Moom's grid sizing boxes.

If you decide you'd like to revert back to the 25-cell maximum, quit Moom, open Terminal, paste this line and press Return:

defaults delete com.manytricks.Moom "Grid: Maximum Dimension Size"

Relaunch Moom, and the old limit will be back.