Call uxterm with a -fn parameter. For example: uxterm -fn 10x20
gives a uxterm windows with a nice 10x20 pixel font.
Use 'uxterm -help' to see more options.
To launch uxterm from the iBar with this fontsize: 'launch uxterm'
Click on the small icon to the left of the title (showing "uxterm", or the current pathname) of the uxterm window
From this menu choose "add to Launcher" and click on "default" close uxterm
Now an uxterm icon is added to the iBar, it is a black square with a white border, with $_ in it in white letters. right click on it. and from the menu choose "edit icon". in the text field Executable add " -fn 10x20" after "uxterm". Click on the close button.
Now you can launch uxterm with the font-size of your choice.
Source: Mahjongg on faqly