Hi, The manual does not list the G18 parameter like the mills do. ( Mills) The plane is XY (G17), ZX (G18), or YZ (G19).

As you mentioned, PB79=1 ( not sure if that is correct but, to change the "bite parameter you would do so in the MDI .
F5 (MDI) enter PB79=1 and press enter, cycle start the parameter will be changed.

Soprtybob