The 9600 is the same feature set as the 7600 and the platen gap is set on the printer itself. Very easy to do. Page 2-19 in the manual, available online.
Press "select type" so PRINTER SETUP appears.
press the > key twice to get to platen gap.
use ^ and V arrow keys to set platen width.
Press Pause to hold the setting. Don't forget to switch back to STANDARD when done.