Change the Default Settings in TextView.

The following are command line options for font setting in TextView:
/font <face>
/fontsize <pitch>
/pl <pagelength>
/rtl (or /ltr)
/charset <charset>
/rawcharset <charset>
/f <filename>

So, for example, you could run in the command line:
textview.exe /font:Arial /fontsize:12 /pl:66 /f:example.txt

To have this as the default settings in your application, you would add the following to your .qxs file:
default.viewer.text: textview.exe /font:Arial /fontsize:12 /pl:66
omitting the /f: <filename>.