Amazingly there's no simple way to control the font size. You can have some control over the font (not size) by changing the theme font (DESIGN tab > Fonts) but you cannot set this on the masters.
This sample from my good friends Echo & Julie's book explains.
http://www.quepublishing.com/article...60223&seqNum=2
If you design templates this is the book to buy (and not just because they are friends and colleagues!)