I personally don't know the old editor with the rich text widget.
So if the Rich Text Widget can also display the Rich Text codes in addition to the What You See Is What You, you can set the font size with the code: \ fs? for font size (where? is twice the font size such that \ fs24 results in a 12 point font). More note information can be found here: http://www.pindari.com/rtf1.html