Another possible solution. One reason that it looks so big is that the default font for the board is set to Verdana, which is designed to look huge. If you uninstall Verdana from your list of fonts, the pages will display in your default font, without having to uncheck the ""allow documents to use other fonts." This would let the Phoenix display at a more reasonable size, while not interfering with other sites where you may want to use their choice of font.
ETA: I just did this, AIFG!
ETFA: Well, not really, unless you like Ariel (or Helvetica), I guess, which are also specified in the stylesheet. If it were up to me, the font face would be dropped from the stylesheet so we could use whatever face we wanted.