Have a look at this thread.
http://www.machsupport.com/forum/index.php/topic,6204.0.html It is a screen I'm working on for a 19 inch touch screen. The idea is mimic the real controller in function and size. The buttons and code window are the same size on hte touch secreen as they are on the real controller. The real one doesn't have a path display but since there were some buttons I won't be needing I had room to add it.

Those buttons end up being about .750 inch square. Hope this helps a little.
Brett