mortbrew,
I have added a CSS customization tutorial page to the
eScape online tutorial. Go to the last topic "Customizing the CSS Stylesheets".
The font size is set to 0.9em, and you can easily change it following the tutorial (I hope - I wrote it pretty fast).
eScape lets you modify your stylesheets (within the predefined selector rules) anyway you like. I think that will solve your problem, but might just make a few more if you go wild with CSS! Have fun making custom CSS files and if there are any more issues or information you want just let us know.