The following settings are an example of how to set up the grid sizes for a 7 inch and a 10 inch tablet. Experierment witht he settings and figure out what works best for you.
To set the grid size go to Menu --> Preferences --> Screen Settings. On the phone screen shots the grid is 5 x 4.
On the 7" tablet screen shot below it is set to 6 x 6.
On the 10" tablet screen shot below it is set to 6 x 8.
7 inch custom tablet settings.
10 Inch Tablet Custom Settings