On a separate note, found the following article which discussed about the Font Sizes and Printing Plain Text in GroupWise:
It appear you can also change the default GroupWise font size in Registry. Not sure whether the end result will be the same, you can try to modify your code to change the registry font size value. The Registry String value usually present if you already setup the font size in GroupWise (Tools – Options – Environment). One side effect to this approach is your GroupWise default font name and size will be the value in the registry.
You do not need to run your code each time on composing message, you can run it when GroupWise startup. Please take extra care when changing the registry value. See the Formativ Language Guide – utilities.Registry() method which provide access to the Windows registry. Let us know if you need some registry sample code.